I once had dinner out with a lady friend who wanted her first mfm and a male friend of mine was with us. Both knew a 3some was the purpose of the meeting. At dinner the chat was purely social and all hit it off very well and the discussion was purely social and they seemd to enjoy eachothers company. As thay had never met before I was concerned there was no chemistry and did not force or even bring up any sexual conversation. We left the eating place and took my 23 ft boat out and anchored it behind ny riverfront home on the quiet warm summer night and still the chat was purely social for over an hour with no moves on either of their parts. I thought perhaps they had no attraction and it seemed the evening would never heat up. So, to see what would happen I went behind my lady friend, cuddled her breasts, she whipped of her top and bra and we both sucked her breasts and as the boat was not suitable for having sex met a week later at a motel and wasted no time in getting down to business!
On another occasion I took a "new to swinging lady" friend to met a couple who were very experienced. All knew the meeting was for a 4some and after some socialzing I started playing with my friends breasts and he followed by playing with his wife's breasts as well. This lead to each couple disrobing ther respective partners as the social conversation proceed and then it was off to bed.
It seems that, though in such situations everyone knows what is planned or anticpated, one cannot be sure if the people new to each other are attracted or not and if they go along with the icebreaker it implies comfort for proceeding with more intimate fun.