Princess Auto and this place where my wagon is from www.toywagons.com offer ski supports for their wagons but it isn't the big wagon like I have but should still fit at least three. You might have some success pulling two of them with only two in each one.

The old fashion sleds with the sides and backs would probably fit two per sled.

If you speak to the teacher of the oldest grade at your son's school they might be willing to ask in the classroom if anyone was interested to take the info home to their parents especially if you told the you would not speak to the student if they called unless you spoke to a parent first.

What is the stop just before your house as in how far the other way or the stop after your house. that would be the best place to find someone. There might be an older child that would walk the extra block to your house for a bit of money just to help put your son on the bus.