It may be anathema to you if you want your kids to build their own alcohol stoves, but my favorite is the White Box stove, ready built for $20 by Bill in Montana. I have used my own built alcohol stoves but after using the WB I realized what a piker I am when it came to stove construction. One part of Zen is realizing when you are in the presence of a master, which is how I felt when I first saw the white box - simple, great design. Yellow Heet or regular denatured alcohol both work great for fuel, with a long burn time. Make sure the kids use a light weight water container for boiling, most alcohol stoves don't burn terribly long and you won't want to spend alot of time heating up metal instead of water.

In the end all the designs should work fine, and the kids should have some fun building their own.