Here's my $5 incentive idea. I was going to make a "pin the pumpkin on the pumpkin patch" game for my son's kindergarten class:
-Carve a tangle of vines with a bunch of small leaves out of 1/4" MDF or plywood, and put 5 spiders in random places on the vines (think of a trellis, just 1/2" wide and more random). Paint the vines and leaves various shades of green, and the spiders black.
-Carve 1 pumpkin for each kid, about 6" wide, spray paint orange/green and let them decorate with markers. Then throw a little loop of duct tape on the back, blindfold them, and let them stick it to the vines.
-If your pumpkin is within 1" of a spider, you lose. BUT, if you completely covered (squished) a spider, you win. Multiple rounds as necessary.
I'm still going to carve out the little pumpkins for them, but there won't be time to play a game.