We worked on and finished the Car project from Crunch Labs today. Crunch Labs is an excellent engineering project kit subscription that arrives once a month. We're almost finished with our first year of Crunch Labs; I think we have four projects left. Overall, this has been one of my son's favorite learning activities. I plan to extend for a second year.
The kits are excellent quality and the instructions just couldn't get any better. The videos are easy to follow and explain the physics behind the project.
https://www.crunchlabs.com/?srsltid=AfmBOoor__130UCrObvvXouQ18hgAUdzf00p-3mZLq1eHsocYrGrRZF4
Here are pictures and videos of the boomerang car my 9 year-old built. There are magnets on the front of the car, so it can move metal objects.