I will be happy to take over your reservations if you chicken out! Our kids are older and we embarrasingly STILL haven't taken them camping. I used to backpack but turned into a wimp when my 1st was born. Haven't stayed anywhere without a dishwasher in 7 years
I would bail and rent a cheap Victorian in Chincoteague.
The oceanfront sites at Assateague S.P. are not too bad and you have the warm water showers.
One tip for folks using the showers at the NP (where the mosquitos wait for you and then attack when you get in) is mix up a solution of water, ammonia and a little dish soap (to get it to stick) in a spray bottle and bring it with you. Spray around the shower, car, water faucet etc. just before you do something there. It knocks them back long enough to get in and get out. They hate the ammonia.