It is probably a good idea to talk about what will make everyone comfortable. For example, will it be awkward who your wife sits next to? Or if she kisses one person in front of the other, will it feel odd?
I was in a FMF triad before and I felt some stress over trying to balance everything. If I snuggled with one woman for 20 minutes, I felt like I had to do the same with the other. We finally talked about it and realized that a lot of the stress was me guessing what they wanted and was not even something that they were thinking about.