That sounds like a good way to put it to me too. There is no shame in loving two or more people. Those of us who identify as poly here understand that fully and are here to back you up.
It sounds like you could create a loving and meaningful "vee" from this situation. Your husband could be a very lucky man to have a partner and a metamour who love him. More love brings more of everything good if you ask me. That's why love should never be scarce I think; always abundant. Go for it!
and let us know how it goes.