Little kids and water parks, Water World at Denver?

Has anyone ever taken little kids to a water park? We have two young boys and are looking for something fun to do with 90 degree weather. They are almost 4 and 18 months. Would a water park be a waste of time for us? We'd go to the zoo but the 90 degree weather is a bit hot for that. Any suggestions of what to do on a hot day with kiddies who need to get outside. We live in an apartment complex with no park so they are stuck inside most days (we have one car). We want our boys to have some fun, but are nervous about a water park.