Balloon Powered LEGO Car If you have the pieces for these (I think we have a couple wheels already), I have balloons. I can print out the directions and have it as a building project activity for the biggers?
Marble Races with a cheap pool noodle (occupies the kids for hours.) Did this, but instead of cutting the pool noodle, the marble is small enough to fit inside the full noodle to roll down. Then can use the noodle for other things too!