Generally none at all, apart from those you would normally make to go anywhere.
Children are natural nudists and usually take to it with minimum adjustment.
Bring towels, comfortable footwear, suntan and sunglasses. You might also want to bring lounge chairs, a hat, something to read and any sporting equipment you desire. This varies from park to park and generally costs less than public RV campgrounds. No, you will not. Ignore them - everyone else will.