i understand your problem,..after more then 18 years of marriage my wife and i wanted to "spice " up our relationship,.we considered swinging but sex with someone we just met seemed far to risky.,.then i found out that a couple we knew and were close with was in the same boat,..wanting to try something new but wanting it safe and discreet.
the only problem,..they were black and my wife comes from a bit of a racist background. even though she liked the guy the idea of "servicing" a black cock put her off AND she felt i only wanted to fuck HIS wife (partly true) ,..but after sitting down and talking it over at length like adults we decided to at least give it a try.,.
after setting rules and the first few times were still awkward and uncomfortable,..i believe that jelousy played a big part in making it difficult,..but we continued to have open and honest conversations between BOTH ourselves AND our lovers until her fears were allayed.
open and HONEST communication is the true key to finding and experiancing a forefilling sexual escapade.,.after more than TWO years we are still involved with the same couple,. my wife discovered that she is a sexual submissive and prefers to be dominated by her "bull",..while i'am able enjoy HIS wife sexually without guilt or jelousy from my wife afterwards.
in fact our relationship has grown so much that only last August we attempted our first "cross-seeding" (without success).,.it seems that we have indeed "fallen" in love with our bedmates to the point of wanting to forefill our devotion with each other fully ,..
this was a personal choice that works for US,.. but OPEN and HONEST communication will also help you in YOUR predicament.