Building and flying custom FPV quadcopters. I think this would be a great way to teach young kids all kinds of interesting topics AND get them to go outside.
I imagine this to be a real-life thing.
In Germany, we have things called "Volkshochschule" (think: community college without any commitment, just booked by the course.
It would be perfect for this kind of model, or just offering a few weeks crash course during the summer break.