I would suggest two things:
Sue all three individuals for defamation of character and take it to a jury. You don’t use a family law attorney, you use a cut throat attorney that doesn’t take prisoners.
Second, though he is more expensive, use Dr. Richard Gardner. He is the foremost authority on identifying true and false allegations of child sexual abuse. You might also consider asking for a consultation by attorney Travis Ballard (517) 263-7822 from Michigan.
CBS 48-Hours featured him handling a case like yours a few years back. Dr. Gardner has a web site, but I’m not sure of the address.
Mostly, get into their pocket books. Make them prove their allegations before a jury, and when they can’t, drain them of all their assets.