The date of your trip could make a large difference to your planning. When will you be going? The Eureka supercharger could be open by the end of July if all goes well, and the Crescent City supercharger (which will be located directly across from Redwood NP headquarters) possibly by September as the Eureka crew will be heading there next. There are a couple of RV parks in Crescent City with NEMA 14-50s, and a car dealer with a J1772, so a stop there to add some charge shouldn't be too much of a problem if you need a little to get you to Eureka. There's also a NEMA 14-50 in Hiouchi (high-OO-chee) before you get to CC. Check out plugshare for details.
I used to live in Crescent City, and even worked on the trail crew for Redwood National Park one summer during high school, so pardon me if this is more detailed that you might be interested in! Redwood National and State Parks are a slightly odd combination of federal and state lands managed together, and as mentioned by cpa, is not the type of park where you go in and then back out again. A drive from Grants Pass south on 199 to Crescent City, then south on 101 towards SF will take you in and out of the park several times. There are many in-out type of drives, as well as several through routes that will keep you moving towards your destination, while taking your charge down more slowly as you won't be driving highway speeds.
Highly recommended through route:
Howland Hill Road & Stout Grove - you might want to head into Hiouchi before this drive - add some charge from a Nema 14-50 at Hiouchi Hamlet RV Resort if needed, while grabbing a bite across the street at the Hiouchi Cafe (since 1931!). Even if you don't need a charge, there is a park information center just west of town where you can get a park map and any needed info - like confirming that Howland Hill Road is open. Then, head back east (it's only 2 miles back to the turnoff.) Just east of Hiouchi, turn south onto South Fork Road. Cross two bridges, then right onto Douglas Park Drive (there are signs directing you to Stout Grove for both). This becomes Howland Hill Road and is gated at night. It is an unpaved, AMAZING drive through massive redwoods. Don't worry about the lack of pavement; it's good quality gravel. I believe motor homes and trailers are prohibited but it's a piece of cake for any car, and you'll be driving it quite slowly. Don't miss the turnoff for Stout Grove. It's extremely short and has parking at the end (often close to full). Stout Grove is one of the standout spots of the park. The little loop trail is fantastic but even if you don't have time to take it, you'll be surrounded by old growth redwoods just parking your car and looking around. After Stout Grove, continuing on Howland Hill Road will eventually lead you out of the park and onto the plain east of Crescent City. You will have missed a beautiful 3-mile section of US 199 west of Hiouchi, but the drive on Howland Hill Road far surpasses it. Howland Hill Rd. ends at Elk Valley Road, where you can turn left 1 mile to US 101 at Crescent City. Turn right onto 101 North to head just a few blocks into town for any supplies you might need. Shoreline RV Park is off Sunset Circle just before 'the split' with a Nema 14-50, and Redwood National Park Headquarters is at 2nd and K Streets. A new supercharger is slated to arrive by the end of summer in the parking lot across the street.
Recommended side trip (short):
If you have the time, check out the 1856 Battery Point Lighthouse in Crescent City. It's a straight shot west on Front Street to the ocean, then left a couple of blocks. Opening hours depend on the tides but it's an absolutely beautiful view even if you can't go over to the island, or take a tour.
Recommended side trip (short-ish):
South of Crescent City on US 101, the last turn before heading up the hill is Enderts Beach Road. Turn right and follow it a couple miles to the end, up the mountainside and into the trees. At the very end there is a trailhead for a longer walking trip down to the ocean, but just before that, at the crest of the road, there are a couple more parking spots and a picnic area, and an octagonal deck with a commanding view of the coast and of Crescent City.
Once you travel up into the trees on 101 South you will be inside the park again. As you descend back down to the ocean approaching Klamath, there is a parking area for beach access, and shortly after that is parking for Lagoon Creek and the Yurok Loop Trail. After that is a break in park property for the Trees of Mystery tourist attraction, which is at least worth a short stop for the giant Paul Bunyon & Babe and the gift shop. They have a gondola ride that takes you up a mountain as well as their original trails past unusual redwood formations.
Recommended side trip:
Coastal Drive - South of Klamath, after crossing the Klamath bridge whose approaches are topped by bear statues, take the Klamath Beach Road exit. It's a U-shaped exit so you will turn left to head towards the coast. You will soon arrive at an intersection with bridge ruins on your right and parking to your left. This is the previous Klamath bridge, destroyed by the flood of 1964. The western end, with bear statues, remains with interpretive signs. The intersection here is the start of a loop, but there is a one-way section at the far end. So, turn left at the intersection to head directly to the coast. Once you approach the coast you can turn north along a one-way section of Coastal Drive, passing the mouth of the Klamath River and then looping back around to the old bridge for a return to the highway. (The way south on Coastal Drive was once a through route down the coast but is now closed to cars due to erosion.
) One attraction along this route is a radar station built during World War II, facing the ocean and disguised as a farm house.
Highly Recommended through route:
Newton B. Drury Scenic Parkway - this is an excellent alternate route that was US 101 until the 1990s. The exit is prominently signed from US 101 South, a few miles south of Klamath. This route is well-paved and well-traveled, with many pulloffs including a full parking area & very short walk to 'Big Tree', and near the south end of the drive is the Prairie Creek Visitor Center, and Elk Prairie Campground, so named because the prairie is frequented by Roosevelt Elk - if you see a bunch of cars stopped along the road through the prairie, this is why. This route is also highly recommended because it will be much easier on your battery - it's mostly level and an easy 2-lane drive (35-45 MPH if I recall), whereas the new highway is 4 lanes but also goes up and down a mountain or two. Newton B. Drury Parkway reconnects to 101 south of the elk prairie.
Recommended side trip:
Lady Bird Johnson Grove - one of the earliest attractions in the federal portion of the park, and a very nice 1-mile level walk through old-growth redwoods. North of Orick, turn left at Bald Hills Road and drive about 3 miles to the parking area. It's well signed from the highway.
South of Orick as the highway approaches the ocean again you will find the last major stop of the park along 101, the Thomas H. Kuchel Visitor Center. This is also the place to get the gate code for the Tall Trees Trail, which is located much further along Bald Hills Road than Lady Bird Johnson Grove. I am not recommending it, only due to time - it is not a through route, and parking is limited which is why you need a gate code. Once they give it out so many times in a day, they stop. The Tall Trees Grove contains some of the tallest trees in the world, and is at the bottom of a nice but steep trail, taking about 30 minutes to get down but around 90 to get back up! The alternative is to take the Redwood Creek Trail from a parking area much closer to US 101. A shuttle is provided between, but this is a much longer walk, an all-day excursion even when taking a shuttle back to your car. (My wife and I did it once; 10 miles one-way I believe!)
Once you get past Orick the RV park charging becomes more frequent, as do destination chargers in Humboldt County in and around Eureka. Once the supercharger opens at the Bayshore Mall you should be all set.
So, that was even longer than I expected it to be! I hope some of that is helpful to you.
