Make constellations in a tube. I actually do this a lot when we have a spare tube for my kids and for my former daycare I would take dark construction paper scraps and just put it around roughly flat and use a pin to push in the outline of whatever the kids wanted...Great reward. They love it. Or you can, as I did for the older kids, let them select the constellation and I would punch it in. Great cheap activity to WOW any child.
Did this today with the boys. They loved it! they put on swim trunks and played with it in the bathtub. Tommy is currently rolling in it saying "my precious, my slimy!" Plus they already have the soap on em, so I just have to spray them down and add some water for clean kids. Who said snow days had to be boring?