I get requests from kids of all ages for personalized signs. This might be a longish project but it would not require any new tools. You can get local shops to help out and in return they get to prospect for future employees.
Contact a couple of mid-sized signshops in your area that do electric letters. Ask them to bring along some examples of can letters, LED & neon, and maybe a small cabinet. Look for one that has a portable Tig that will come to your school and show the kids how the process is done - maybe allow them to try a couple welds.
Ask all of the shops you contact for any scrap opaque white acrylic, aluminum, and jewel-lite trim. Youll get some ugly colors but the kids can repaint them to whatever they want.
Using pop rivets, double sided tape, scrap vinyl or even screws the kids can make simple shape cans. If you have a metal bender thats great - if not you can bend the .032 aluminum on the edge of a table with a hammer.
Cut the Acrylic with coping saws to simple shapes that the kids design themselves. Get the sign guy to show you minimum radiuses for the trim cap.
The kids can use colored transparencies, paint directly on the acrylic or put photos on the acrylic for the designs. If you keep the cans to less than 11" x 11" so that you can light them with a lightbulb (another lesson plan there with donations from your local home depot) I will throw in transluscent digital prints. Provided we are not talking about 1000 kids here
You might be able to get one of your local shops with a printer to do this as well. Remeber to start with the design first - then make the can - then cut the acrylic.
Edit - i forgot you mentioned you have a CNC - use that to cut the acrylic faces - BONUS!
That should give you a couple classes for the demo, metal work, acrylic cutting, decoration, and electric wiring.