My Mrs (accidentally) let one rip during a quiet moment in the book study once. Both my children, and myself, were so embarrassed! We didnt want to breathe either! hehe She has a habit of doing that at the most inopportune moments!
Jesika, Try not to give your kids too much attention with their little game. You seem to be fuelling them to do it all the more. If they continue just tell them they stink (in a light hearted way), and if you`re in the car just wind down all of the windows, or if theyre inside tell them to go out. Its a phase that boys seem to go through. Some never finish it though - that might happen with your little angels if theyre rewarded with attention.
Mike.