This is a really great idea (and honestly, not just helpful for kids but... have you poked your head in some of the beginner's crypto groups lately?), and sounds really fun.

Can I suggest ICX, Icon, for I, or XRB, RaiBlocks, for X? Both are interesting and promising coins.

And if it really needs filling up, I'd also suggest ONION, as it's a great privacy coin

ICX XRB