If your friends have any older kids, maybe 10-12 years old, let it be known that you will pay them to help babysit the younger kids. Some of your friends will be worried that there are not enough babysitters, or that they don't know the babysitters. If your friends know each other, they might feel better about leaving their kids with the babysitter if they know the babysitter's parents. Still hire at least one professional.
Gonna win 'em all!