Have them set up a minecraft server with spigot if you have the 4G version. And then they can do mods and even make the server available over the internet if you can set up port forwarding and stuff. Yeah, not the most programming heavy task, but it's a good example to teach kids how these services actually work.

What do your kids like to do? Any chance you could integrate a computer with it? My daughter loves to cook and dance and I haven’t found a way to integrate that with computers but she’s happy so I haven’t pressed it.

RoboCup Junior OnStage is a good example of integrating dance with computers. You can program sensors to detect triggers from humans and respond by moving props into place. There's a lot of freedom to choose what type of sensors, computers, and actuators to use. Search for videos of RoboCup OnStage to see some examples.

You could hook it up to some midi instruments

I tried that, the delay was too high to the synth. Not sure how to fix it.

Look into Kano computers. They come as set of RPi, display, case and battery. Then kids assemble their own "tablet".

There are endless possibilities. Kids would likely appreciate something like creating a console game emulator or wiring up hardware sensors to the raspberry pi.

It doesn't exist, afaik, but a Rocky's Boots would be a nice thing to have on a pi.