Found this idea on Pintrest- so simple, yet extremely entertaining for the little people. All you really need is baking soda and vinegar. I added food coloring to the vinegar at first, but the kids went through it so fast they were using unaltered stuff towards the end. It didn't seem to bother them one bit :)
Yes, the booger suckers were all brand new, fresh out of the package... The kept this up until I had to call them away for lunch. It lasted a good 30 minutes. I thought it might be fun to try it outside on the driveway next time. Dump the baking soda right on the ground and let them go.