Last November 3rd I showed a pile of 30 Cajon kits finished and ready to be delivered to a local school. It was a big job for a small shop space dealing with the sheet stock, and a bit repetitive too.
Today I went to the school to see have the kids were getting along putting their kits together. As with so many school activities the parents financial contributions have been slowish to arrive and so not all the kids have their kits yet. The drum above belongs to a good little boy that was the first in the class to finish. All that remains is whatever wild paint job he decides. He can also really play the cajon. I opted for 1/8 ply for the front and I feel that contributes to a fine sound.
You can't imagine the chaos of the class room with about 12 kits in various stages of assembly. Some of the kids have never held a screw driver or driven a nail, but they are right in there making it happen. I supplied the kids with clamps for assembly and a hand plane to trim the edges once it is all glued together.
I've been promised photos of the fully finished and painted Cajons. The sound of the drums is remarkably good so I suggest the cajon as a basic wood working project for you and your kids.