I think you could manage Mary having more than One wolf's litter without making it into a three+-some, As you said, wolves are wolves, its entirely possible she might go through 2 wolves before she finds the Alpha she's happy with.

Uh, no. Telepathic bond means when she feels the urge to mate, so does Heero, and so do the partners of the wolves who fall in with her. It's pretty much a Wolves Made Them Do It scenario. Lucky she's only in heat twice a year and the rest of the time she couldn't care less.