Toca boca has a ton of really great kids apps. The newest is Toca Blocks. This app is great for someone who is interested in building structures, designing interiors, and planning out a town, all with signature Toca whimsy. Toca Blocks capitilizes on the immense popularity of Minecraft, but it's simpler and prettier, so more appealing to a younger crowd.
Similar Apps to Try:
Build a Truck by Duck Duck Moose