Just pitching in with the terms
Polyandry is when there are several husbands for one woman, in your case it doesn't apply since the two males would be involved together too, in which case it's more of a group marriage or, leaving marriage out of it, a triad.
Polygyny is the equivalent with several women for one man, and the most well-known for of polygamy.
And as redpepper said, polyamory is the term that encompasses all of that, and more, and where marriage or the lack thereof is irrelevant
I hope that's helping you a bit with the terms. It's a lot of new vocabulary to get used to ^_^
That looks like a pretty good situation... Well, apart from the fact your friend is moving, but it looks like it went very well with your husband. Another point for honesty and openness! I hope everything turns out for you guys.