I would think that 9 months old is a little young for a local park, they don't have the same health and safety concerns as they do in the U.K. Your Grandson will love the pool, the beautiful fresh fruit and vegetables as my Granddaughter did at 11 month old, she also enjoyed all the attention she got.
We bought our Granddaughter one of those push along plastic buggies with the parasol on the top, they are shaped as animals and if you press the button on the top they play music. She loved that. They are really cheap in lots of shops in Fethiye.
Tell your daughter there are no nappy bags in Turkey, so she should bring some with her.