Convention after-party turns into swinger couple inviting (M)e to join them. (M/F, another M watched)

Howdy Reddit! Long time first time so bear with me as I am by no means a writer but had to share this awesome encounter I had over the weekend.

It began late Saturday night just as a huge convention was starting to wind down and the heavy drinking began. I was with a co-worker, another dude, on the trip and around 2AM my buddy was way way too drunk to continue so I helped carry him back to the room and while on the way back down the hall I saw a hotel party in full swing. "com'on down guys!" the room yelled but I said sure and carried my friend inside, made sure he was face down on the bed and a bucket beside him just in case. So i went back out to the hallway because i wasn't ready to be done for the night.

Walked down the hall to the hotel party and this older woman maybe late 40s about 5'7" dark brunette MILF with big tits was walking up at the same time in front of me and did a sort of flirtatious shimmy. She was wearing like a silk teddy with her boobs essentially hanging out, and her husband proceeded to lift her shirt from behind her and flash me. "awesome." I said and fist pumped and walked to the hotel party.