Wife and I tried this with a FMF last weekend. Wife's friend laid on her back on coffee table, wife straddled her in a 69 position, I went doggy style with my wife while she was eating her friend's pussy and her friend was licking my wife's clit, and licking the pussy cream off my shaft and nut sack.
Was so unbelievably HOT - I had to pull out several times to keep from cumming, but each time I did her friend hungrily took my cock in a deepthroat, so I actually had to walk away a couple times (shame I had to then watch the ladies eat each other's pussy with total abandon!).
Wife said it was incredibly hot feeling her clit and pussy lips being licked while being deeply filled with hot cock from behind - and her friend's running commentary on how hot her pussy looked with my cock sliding in and out about caused us BOTH to get off early!
My wife had multiple orgasms, and I ended up blasting a HUGE load in my wife's pussy while her friend was milking and sucking my balls (which also made my wife cum very hard, shaking and moaning), then our friend licked my cock and balls clean, too. Just when I thought it was over, our friend turned her attention back to my wife's dripping pussy and sucked and licked every drop of my load out of my wife's cream pie. We then rewarded our friend with two tongues on her clit at once, followed by a deep fucking and another HUGE load blown balls deep in her pussy, with the wife milking my balls and kissing me and talking nasty in my ear.
I recommend this method - don't know about the MFM situation (wife hasn't wanted that yet).
My $0.02
Mr. Williams