Well there is the Water Park at Calis, which is about 45 minutes away. Although they wouldn't be big enough go on most of the water slides, there would be lots of other children.
There is a childrens play area at Sugar Beach, which is at Olu Deniz.
The turkish love children, so they will be spoilt rotten

our kids were about 3 when we first went to ould. the waterpark in chalis is lovely lots for a little one to do little pool with slides a park so on. thers horse riding in hisaronu she/he can ride with you or have their own horse. Suger beach does have a nice play area you pay once and can go back and for all day.the beach there is also very shallow. Theres also a bit of a funfair now in hisaronu. (which is about 4-5 mins away by bus)

there is so much to do lots of excursions but dont worry until you get there there are loads of places in olu and hisaronu that will arrange your days out just shop around for the best prices
check my website for more information and prices through hamish mcturks

Thanks for the suggestions will definately do the water park and sugar beach. Which boat trips might me suitable for him?

the water park at grand ucel hotel ovacik is far better than sultans aqua park calis ands its cheaper
http://www.granducel.com/hotel/aquapark.html
hope this is of some help

This is the largest Aquapark in the Feythiye area with 6 new slides, a childrens splash pool with octopus slide and a jacuzzi pool and swimming pool.