Profiles and online communication offer only hints at how a person really is. Even photographs show little depth. Quick meet and greets are an easy way to filter for prospective play mates, and can save a heck of a lot of time over back and forth e-mails, chats, and phone conversations. You get a much quicker read on chemistry in person than via any other method. So, I think you're idea of meeting four of them this weekend is a great idea.
My wife and I are venturing down the MFM pathway right now, having experienced couples before. We've been in contact with a few single men, but haven't met any just yet. We expect to meet a few of them in the coming weeks. My wife asked "What if I like all three of them?" I said, "Then have sex with all three of them. There's no quota here!"
Approaching them is easy; just put out feelers voicing some interest in them. Since single males are in an oversupply situation, you'll probably get rapid responses to the ones you do contact. Rejecting them is easy as well; just the same as you would with a couple. Polite, but to the point; "We enjoyed spending time with you but did not feel the chemistry was there to take this any further. Thanks for your interest. Bye." I wouldn't worry so much about hurt feelings. Regulars in the lifestyle know there is going to be some rejection from time to time. The non-regulars, well they need to learn
Just be polite in your rejection.
I concur with BiloxiCouple's assessment of Trucker. Major warning flags popping up on that one. The other three, see where it goes.