If they like to tinker, they'll like this fantastic physics game/simulation!
A fantastic physics simulation with challenges that increase in difficulty. Many will only take a few minutes but there was one that my 9 year old son & I spent approximately 6 hours working out a clumsy, but functional solution. For a while, it seemed downright impossible. But that's the point, this app beckons you to go back & try again. We soon stumbled upon a much more elegant and simpler solution. My students (college age) often lack the tenacity & persistence to stick with a difficult challenge.
This will be good practice for young kids to learn that persistence pays off.
How I Use It
Don't just let the kids get by with creating a working solution. Take it up a notch by asking them to give a report on a challenge they solved explaining what they tried that failed, and what finally worked. Ask if more than one solution to the same problem was possible, and if so, what techniques gave the best result.