I had been involved with 4H for 14 years. The first year guilters made a wallhanging using half square triangles. Use the pencil lines stitching on either side along the center diagonal line. Then cut apart to make two blocks, repeat once = 4 blocks. The youngsters can then arrange and rearrange them to suit. Sew the blocks together, add a border, sandwich and then handquilt. Use a marker to show the quilting lines emphasing the importance of keeping the stitches even in size and as straight as possible. AND have them write on the back as in making a label.
Use the tape or a stack of post-it notes as a seam guide, and have an instructor along side guiding and slowing the machine with their hand on the handwheel.
Good luck. This is a rewarding endeavor and the kids will love it.