Advice on not screwing up a newly opened marriage
I've been in a faithful, monogamous relationship for around 20 years. We have occasionally talked about boundaries and other people. The rules evolved from "if you were to cheat once, I probably wouldn't leave" to an explicit 'don't ask, don't tell'. I never met anyone else under those rules because I never found an opportunity that could be taken without deception--at minimum I'd have to lie about where I was going.
Recently things have changed significantly in a short time. Listening to a Dan Savage podcast sparked another discussion where we discussed her fears and how to reduce them, with the result being that I can openly look, openly date with her full knowledge and cooperation, but subject to her veto. Wife prefers to remain mono for now, possibly forever.
I updated my profile on a couple of sites, and was contacted by P, a woman in a long term poly relationship. I initially misunderstood, and thought she was recruiting for a local poly group rather than being specifically interested in me. We got that straightened out, exchanged texts and emails for a while, and Wife and I met P and her husband. That went very well, so P and I are going to meet for lunch in a week or so and see where things go.
The relationship with P appears to be heading in a direction almost exactly what I really wanted--I thought I was going to have to settle for very casual outside relationships with little emotional connection in order to keep Wife from worrying. Since P's primary relationship is also well established and long term, that's much less of a worry for Wife.
Part of me thinks this is too good to be true, there's got to be a catch. I guess what I'm looking for is advice on how to make this go as smoothly as possible. Any obvious mistakes I appear to be making, or things I'm overlooking?