Choose one child to be Tow-Mater. The rest of the children will be the tractors.
Have the tractors spread out in a single row. Then have them make a bridge with their body by doing a back bend. If this is too difficult for your guests, have them stand with their legs spread far apart.
Tow-Mater must try to tip the tractors down! He does this by crawling under one of the bridges. If a tractor falls over while Tow-Mater crawls through they are out.
Tow-Mater can only crawl through; he cannot push, tickle or intentionally nudge the tractors.
After Tow-Mater goes through all the children once, have him crawl under a second time. Continue until only one tractor is left standing.
The winning child gets to be Tow-Mater in the next round.