I should add that if your wife is willing to try this you are 99% of the way there. Check out that site with your wife and see how many people are into that in your area. I think you will be amazed at how many local members you will see there. You can join for free and once you join you can read their profiles and see which couples (or individuals) are possibilities for you. I think most people will want to get to know each other a bit first in a social setting before committing to anything sexual.
Good luck, as I said before, we would luv to hear how it goes.