The North Jersey supercharger is off the NJTP and I stop there frequently. It's usually empty, or maybe one other car there. I certainly have never had to wait there. Although if you are driving north on Wednesday afternoon (like everyone else), you may see a few cars there charging.
The southern CT SC is off the Merritt Parkway, and was a very early supercharger installation (2013 or 2014), so they weren't building 12 and 16 stall locations back then. It's also a very very very small rest stop and very limited parking, and the SC stalls are frequently ICEd. But there is high turnover there, so if there are ICE cars there, they usually move within 5 or 10 minutes.
(edit: Tesla might have routed you to the Darien SC off I-95 which is also 4 stalls, but not as crowded. Either way, I'd strongly suggest the Merritt Parkway route instead of 95 ESPECIALLY on Thanksgiving weekend).
The Delaware location was also just four stalls when it first was built (even before the CT location, it was one of the first on the east coast). But then they upgraded it to 12 because it's such a popular route.
I've driven up and down the eastern seaboard too many times to count, and even through NY/NJ metro area, I've never once had to wait for a supercharger.
Finally, there are many other SC options along your route. Don't just take what the Tesla Nav suggests. Try using:
A Better Routeplanner which is much more flexible and accurate.
For instance, if you get a full charge in Delaware, you can make it up to Paramus, NJ to charge, and then take the Tappan Zee bridge into Westchester, and charge again at Tarrytown, NY. Then from there make it to Auburn, MA. There's dozens of routes and SCs you can use.
Good luck!
