Poly basics most people don't know:
1. Each person has their own relationships.
2. Triads (where three people have relationships with each other) are very rare in polyamory and are very hard to make work long term.
3. If one person in a couple has more than one romantic relationship, BOTH are practicing polyamory, whether the other dates others or not.
4. Polyamory is LESS about being comfortable having more than one romantic partner, and is MORE about being comfortable with your partner having other partners.
Keep these things in mind when discussing with your wife, as you'll BOTH have to do a lot of work to make poly work. And if she chooses not to date, but says you can, then she will be doing lots of work for only your benefit, and you'll be doing a lot less work and won't really relate to what she's going through.
Mono/poly is doable, but really hard and is only a positive experience in select cases.