1.) I've never been the exact week you are talking about in May but I have been the week before and after and the crowds are average in my opinion .
2.) As far as the water park is concerned , I don't think either one is better for small children . They both have alot of things that are great for small children like kiddie slides , low water areas where kids can sit and sand for them to play in which my kids love. We always buy them a shovel and pail at the park for them to play with & the kiddie lunches at both park come in a bucket with shovel also for them to use. We've been taking DS5 since he was two , DD3 since she was 7 months old and DS2 since he was 3 months old , every year to the water park , hope this helps.