Look at plugshare.com and see your other charging options. Buy yourself a Chademo adapter. You may never need it, but it is always good to have. Then make the drive and see how it goes. Stop and charge if you need to. My experience is the trip planner is overly conservative in the beginning and is more accurate after a few miles of driving.
Or drive a little slower and find a Level 2 charger along the way, where you can have a nice meal and add a 20-mile buffer. I got my S85 in early 2013, and until 2015 there was no supercharger on a 245 mile route I take from Boston to the Adirondack Mountains 4-6 times a year. I learned to drive a little slower and we discovered the town of Montpelier, VT, with two L2 chargers and some nice restaurants, coffee, gelato and other shops to visit. Vs. our former "pit stop" approach for gas and fast food. It took more time but made the trip much more enjoyable.
Of course, now there are FOUR Superchargers along the route (Hooksett and W. Lebanon NH, Lincoln and S. Burlington VT) and a fifth (Plattsburgh NY) not far from my destination - and we're back to stopping at McDonald's or Panera while Supercharging the X. :-(