I would love to do this, any advice ? Screening process,how many people to have fun & should be considered ?

The point that you need those questions answered tells me that you probably aren't equipped to pull it off.

It's not clear if you're male or female, but most M&G's are run by people that are known in their community.  Then, they extend invites to people that they know, or can verify through others.

Invite more than you expect to attend.  Invite more females than males.  Have it at a place where people will be comfortable, and not bothered by outsiders or neighbors.

Sounds like a blast Im in

FYI...There is a m&g for swingers on Wednesdays @ the 94th Aero squad out on the patio/bar...would not be too much of a stretch for a dual m&g...not actually connected, I know swingers don't necessarily like the hoby but they always limit or exclude single men from their groups and for us that are former participants etc. it's a real bummer to not be able to attend...And I'm not going to pay a grand for 5-6 hrs to have a willing partner just to get in the door