If it's at the same place, they launch out of a marina. I guess it would depend on how the marina owner feels about people camping in his parking lot.
Of course, right next door is the old resort they used as a launching point for the '96 Olympics. Last I saw, it was boarded up and had no running water.
You could probably get away w/sleeping in your car, but the no-seeums would carry you away. There are bathrooms w/water. I can't remember if there are showers. I think there are a couple.
No, you don't need to pre-register. Sleeping in a car is probably the best bet if you want to be very close. I am pretty sure there are 2 or 3 showers on site.
I stayed with Eric Oetgen last year and may try to stay with him again this year so I have no idea about hotels in the area.
Well the Sheraton hotel you are thinking of has been converted into condos. There may be a few available for nightly rental but that is going to cost you a ton. There aren't really any hotels I can think of around the launch site at Sail Harbor. Sleeping in your car or finding a friend to stay with is probably the best bet. Wilmington and surrounding Islands are primarily residential thus the lack of hotels.
PS: I hope you all enjoy your stay in the city TLF is based out of!