The Freddi fish games by Humongous Entertainment are really great at that age. They are simple point and click adventures by Ron Gilbert with fun characters and

The Freddi fish games by Humongous Entertainment are really great at that age. They are simple point and click adventures by Ron Gilbert with fun characters and a lot of interaction on the screen. Easy to get for cheap on Steam or sometimes in bundles and I've been impressed with how quickly it developed puzzle solving skills with my nephews. Once the child is a bit older, the Pajama Sam serie is also great.