In our local grammar school, the third grade class make quilts each year. (or they have the option of making their quilt top into a pillow). They select their fabric and are given a supplies list. Since I now have 2 nieces that have been through this program (and nephew will be coming up in another year or so) I've had great fun and practice with this. The project takes 1 week of one class hour per day.
The class teachers have no clue as to what is involved. They give the kids a cardboard template to cut out a solid block and a patterned block. (They do a very small quilt with alternating plain/patterned fabrics). The kids don't get the cutting part. I usually end up bringing home all the fabric and cutting it all out with my rotary cutter the first night. Also mark sewing lines on their blocks. There is no machine available to any of them - all hand piecing. Some of them are pretty diligent about their sewing...others not so much. Since they only have the week to complete the project it can get a bit hectic. After they have sewn all their blocks together I usually bring the tops home and reinforce the stitching where needed. I also bring home and machine sew the backing/batting to their tops or pillows. They then hand sew the turning openings closed.
For your adventure I'd probably do all the cutting and use an alternating plain block with a 4 patch block. About 6 or 8" blocks. Little hands/fingers might have issues with small pieces. And if it's a tedious pattern they might get bored quickly. Something small like a cuddle quilt could be done in a short period of time.