I find it so overwhelming looking for suitable places, even with the filters on you still get totally unsuitable options and there's just too many of them. It took two days of DH searching to find Almirida in Crete, I gave up on day 1...
What sort of things does your DS like doing? If he enjoys swimming pools and swimming in the sea, most Greek islands will have somewhere that ticks your boxes. Kefalonia is lovely.
We love Corfu, but we like to hire a car and go to Aqualand, the donkey sanctuary, Corfu Town, old Perithia. We also have a day hiring a little boat to ourselves and chug down the coast to quiet coves and lovely tavernas for lunch. We'll have a quiet day locally snorkelling or reading on a beach, then a busier day with a bit more bustle. Some beaches have those inflatable assault course things on, vast majority have a few tavernas or other eating places on, and people come round in vans selling fresh fruit and the like.
It makes a difference what you want to do with your time. AI hotel will be lovely but you could be anywhere with nice beaches. Self catering in a villa or apartment and eating out in local restaurants, you're very much in Greece and supporting local economies. There's something to be said for both.
Greece is magical. The Greeks are a lovely people.