How do I game with this situation?

I'm in a LTR with a girl who wants to add another chick to the mix. She's a bit shy and I'm not certain how to go about picking a third up. It's happened a couple times in the past but typically through websites where you have to sift though a bunch of guys posing as women or meeting up with people who are not the same as those pictured. We'd both rather go out and find someone we are both attracted to but that's where we get stuck.

I don't see any information on how to be a good wingwoman or maybe I need to be the wingman for her. The other deal is that we aren't looking for a traditional LTR out of the deal so I'm not certain if the whole set them up for a date later on really works.

We are in an area with lots of tourists so that may help a bit but I still need some help with getting started. Oh by the way, we're married to each other so do we go out with rings or without?