Regarding your wife, you may be able to claim that she didn’t intend to live with you (part of the application form, I believe) given that she filed for divorce as soon as she arrived.
When it comes to the kids, I don’t know all the details obviously but I’d encourage you to get another DNA test (has she admitted the possibility that they’re not your biological children?). And maybe go talk through the repercussions of stepping out of their lives entirely (for you and them) with a counsellor. I mean, it sounds like you’ve been loving them as your own and bringing them up for years so I mean, I can’t imagin how awful this all is but I’d hate for you to miss out on the relationship you’ve already built with them because of her. And for them to suddenly lose you when it’s not their fault either.
Anyway I’ll end the totally unsolicited advice here and just reiterate that the application includes stating that you intend to reside with your partner so proving that she was planning to ask for a divorce may be easier than proving that she only married you in the first place for visa reasons. But I agree with others - you need a specialised immigration attorney.