Advice on Triads?

My husband and I have been looking for a third for a little while now and found one lead but it didn't pan out. Recently I've gotten in contact with someone I've met at a few cons, and i know I would treat like a princess (as every girl deserves to be treated), and I know he would too, provided she agrees to our terms, which would be not being affectionate around his daughter or being around while she's here at all, and it would mean not bringing weed over here (she has a medical reason for it), and I'm not sure how to pitch the idea to either of them. I know my husband would be open to it if he met her, and we all talked about it and our expectations and rules, but it's how to pitch it to her and see her opinion on joining our relationship, or any relationship for that matter.