My first threesome and my first time in front of other people [FM] [MFM] [M18] [F18]

When I was eighteen I used to date this girl who was very open minded. I had two relationships with her two years apart.
One time I was having a little party with my friends, we were like six men, and I told her to bring her friends, which I knew were very slutty, they would usually talk about it very openly when I was around, they would even call each other slut.
The house wasn’t that big. Only two bedrooms, the parents’ and my friend’s (which had twin beds). And we were all pretty touchy people, pushing each other around when drinking, and the such. Obviously everything very flirty.
In the heat of the night I said “me and [gf] are gonna go to your room [owner of the house]”, and I took her hand and went to the room.
But when I was walking, another friend said “hey, can I go to your parent’s room?”
The owner of the house replied
“No. If you guys want to fuck you can only use my room”.

I said to him “you guys wanna wait?”, and then added, joking, “or you can fuck on the other bed”. My friend looked at the girl and she said that they were really good friends anyway (she and my gf). So we all went into the room.