Grind the bastards into hamburger meat and feed them to the alligators in Florida. They aren’t worth any more than that.
At least for Mitchell, skip the grinding and just hand him over to the alligators, kicking and screaming. He deserves to see those jaws coming at him -- finally, a creature he can't manipulate.
I think Wanda is seriously mentally ill, and she seems to be responding to medication, and being cooperative. Keeping her permanently ensconced in a secure psychiatric institution is good enough for me. From Elizabeth's testimony, it sounds like Wanda was being manipulated and exploited by Mitchell, much as Elizabeth was. They were both mentally weak -- Wanda because of mental illness, and Elizabeth because of youth, inexperience, trauma, and we learn now, forced drug and alcohol intake as well -- and Mitchell was a determined and experienced exploiter.