Oh, this was the most exciting (and the messiest) project this far. M loved it and returned to it the next day.
The project itself was simple. I had 3 old socks laying around and some old sand from the sand box that we recently turned into a pool. So we filled the socks with sand, dipped them each into paint and splat-splat-splattered them all over a piece of butcher paper.
And then I turned away to answer the phone and came back to the splat-splat-splatters all over the deck (it's a washable paint, so no worries). My objections were quickly overruled as M said he was busy decorating for a party. Hmm, after some negotiations we agreed to limit the decorations to a big banner.
All in all, a really successful art project and we might repeat it next week. Or we might do something new. There are a ton of big and messy projects left in Mary Ann Kohl's book after all.