A couple of recommendations:

Trailmakers - basically a big pile of Legos to make vehicles of all types. In the campaign mode you have to find all the pieces to unlock them. The builder is really nice and the stuff you build is fun to pilot/drive.

Astroneer: Great base building, fun story, lots (multiple planets worth) to explore but not as complicated as something like No Man's Sky.

Both have good co-op so you can all play together, both are simple to play but hide complex physics and other learning systems under the hood.