I would hope they might have changed some in two years, you never know. At minimum they must be having some of the same thoughts you're having about you that you're having about them so are also planning to go slow and not rock the boat? They are finally coming so must want to see you all more than they want to stay away so give them credit for that.

Like Rhapsody says, go slow and concentrate on what you are doing and saying, not on what upsetting things your mother-in-law is up to. You can't do anything about her personality. I'm surprised, if you don't care for her ways that you've asked her over more often than they've been willing to come? I know they're your in-laws and you may love them but most people only invite friends over any more than they have to.