I was there in March with a family with 6 kids aged 0 - 11 and they loved the waterpark at Reunion. I think it was 5pm that it closed the day we were there and stayed till closing but there's other pools in the complex that are opened later. I've also stayed at Windsor Hills and the pool is nice with a big water slide. I will say that the waterslides in Reunion are pretty tame, not as big as the WH one.
There's also lots of planned kids activities at Reunion but not at WH. But some of the activities that involved a craft had a charge of a few dollars. The most expensive was building a stuffed animal (Build a Bear idea) and that was $15. per kid if they wanted to do it.