Have been to Rapids three times now with teen and tween and since we don't have anything like that in the NE where we live, we think it's great. Both times we have gone in the summer and even if it's really hot out, it's great because you can just stay in the water all day.
I would recommend getting there when it opens (10am) for two reasons: a) getting in a bunch of rides before the lines start getting ling and b) enjoying the place before it gets kind of dirty as these places do as the day goes on.
You will get a lot of exercise since the park is pretty large and you have to climb a lot of stairs to go on the really fun big rides. However, there's plenty of less taxing stuff for little kids too.
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