That's great! how old is he?
If he plans to do an other one let him use the sewing machine. My son made aprons for several family members last Christmas and I pinned the fabric with safety pins and drew clearly visible sewing lines on the fabric.
He had a blast using the machine. I did help guiding the fabric occasionally but most of the time he managed to sew close to the line. Just make sure he's not tired and stays focused.
My boy gets easily distracted by technical stuff and it's better to use a really simple sewing machine. Otherwise he tries to figure out what the different buttons do while he's sewing.