Hi Raven, Im new here, but thought this link might help since I was just reading up on it myself. Garter stitch seems to be a commonly used stitch for felting so perfect for a beginner, I imagine the only help the children would need is with the boiling water or the washing machine, which ever method you end up using.
http://www.woolcrafting.com/boiled-wool.html
Heres the thread on the forum I found the discussion in, which would be worth a quick sqiz too.
http://www.knittinghelp.com/forum/sh...d.php?t=101559