My DS is 9, and he loves park paddling pools/splashzones. Always has done. I have noticed a few signs and mentions on websites that suggest over-8s shouldn't be using them which (particularly on hot days) seems a bit mean. I can understand over-12s being frowned on, but a 9 year old is still a kid and, as long as he's careful not to barge into or scare the little ones, he's not doing any harm.