If you have children aged 5-10 and want to get them interested in physics and engineering take a look at Crazy Machines. The game has 102 puzzles that have to be solved by making various contraptions with magnets, pulleys, gears, motors, generators and so on. Some of the physics is somewhat questionable but they get the basics of Newtonian mechanics, friction etc. right.
The only problem with the game is getting it running. We had to turn on some DirectX extensions that had been turned off to get another program to run.
The same version of the program runs on Windows or Mac.