I"ve had many MFM play dates. I used to put ads on CL looking for woman that wanted to have a 2-man erotic massage/adventure, and had many responses. For my male buddy and I, it was always about giving the woman pleasure...from the massage up to whatever the moment turned into-- You can't set up any expectations for yourself, either. If you keep the goal as giving the woman a good time, things should be fine. I'm straight but not phobic at all---in fact, I find it exciting to see other hard cocks.
We did this many times, and it even turned into a few of the gals asking for more guys--so we had some gang bangs too.
Good luck, be safe, don't set up expectations (ie: now time for blow job, etc---let it flow)