You can have him help with things like making sugar scrubs (
this one is nice) and melt and pour soaps.
Make bookmarks from his paintings - especially nice if you do a crayon resister first and then watercolours. Or frame them, make greeting cards or calendars with them.
Have him put hand prints on canvas bags, tshirts or aprons. I made really nice bags with my young kids once. I cut a square out of a plastic grocery bag and taped it securely to what we were making. Then I let them paint the square with acrylics. When I pealed off the plastic when we were done, there was this groovey abstract picture. I outlined it in black and wrote their names and the dates on it. They really look great.
Make stuffed shapes out of cotton or muslin and have him decorate them with fabric markers as gifts for his friends. You can help him add felt eyes for animals after the decorating.
Make beanbags. He can help sew them and stuff them.
Make contact paper and tissue paper stained glass. You can cut them into pretty shapes for Christmas trees or windows.
Make birdseed hangers - have him help mix birdseed and lard and then shape.
hth
Karen