One of the primary ways to turn your kids onto science is to train them to think like a scientist. You want them to try something, then make a little change and then try it again and notice the difference. By the way, the same is true for engineering.
Take paper airplanes for example. You make one, throw it, and see how it flies. Does it go flat and level? Does it turn? Does it rise, then stall, and then nose dive? Now refold it with different sized wings or bend the wingtips up or down. How does it fly now?
Be sure to only change one thing at a time, that way you can build up and understanding about cause and effect. Adding weight to the nose does this. Throwing it hard does that.
Here’s a short video showing a paper airplane design that isn’t too hard to fold, but which flies really well. I also show some of the things you and your kid can change during your tests.
Enjoy!