you're over thinking it, man
I wouldn't see it as not cleaving unto my wife to also have my MIL there (or anyone else my wife would trust to be there). My MIL (and other people) was invited to our sealing, our sealings to our children, the blessings of our children (but not in the circle, I'm not mpfunk), our court appearances to adopt our children. Her presence (or anyone else's) there didn' take away one iota from my wife and mine's experience.