Blowing bubbles with a straw in a pan is probably nothing new, but it never ceases to amaze me what a kick the kids get out of it.
You can use a store bought bubble solution, or just dump some dish soap, and water into the pan, and trial and error it until you have a good bubble mix. I found one part dish soap to eight parts water, works pretty well.
You want around a 1/4 inch of solution in the pan, so the straw can be in the solution, but not touching the bottom of the pan. You get the best bubbles that way.
I'm always worried someone will suck the solution in, instead of blowing out, but it only takes one taste, and the lesson is learned.
As far as kid activities go, the mess factor is pretty low, too. The worst case scenario is a pan getting dumped over, and you having a head start on mopping the floor.
It's great to be a homeschooler.