The boys really loved doing this because I had to buy them packs of gum! It took roughly forever for them to blow a decent one at the same time or not have one kid popping the other one's perfect bubble.
580EX II in 24" softbox camera left 1/2 power
AB1600 in 30 degree honeycomb 1/4 power behind subjects left for rim
AB800 1/2 power camera right medium sofbox
triggered via Cactus v4's
added "clarity" setting in Topaz after extracting them and putting on the blue background (it was shot using a black muslin background)