I did mine a little different than most, I think. I cut my pieces 6 inches wide and different lengths. I then put a 1 1/2 inch sash in between the random lengths, then after a row was finished I put a long sash and then did another row of lengths. That accomidated a lot of different prints and turned out really nice.
My kids were 7, 8 and 9, but I am sure other ages would enjoy them too. :)