It’s hard and most times a fantasy theme. So first things first. You both should thoroughly vet a group of the count of your chosing. Meaning get to a point of trust these people with you and your wife’s safety and well-being. It may take several talks and in person vanilla meets.
Second, clean std sti tests for all within a close time prior to setting up the session. Require proof. Not word of mouth or just trust me etc.
Clear boundaries and expectations.. Do you want them cummimg in her on her on you etc. ? Are there absolute no’s with regards to whats allowed?
Use a hotel as safe common ground rather than your own house.
Recommend having a close friend act as a security bouncer of sorts in case it’s needed. Things get crazy in the moment and you want to have the upper hand for safety.