I’m thinking about having a foursome with my friends but don’t know how

My friends and I are all about the same age 24y, and we frequently travel together to my house in the countryside. This idea started when I saw some messages between my best friend and his girlfriend talking about having a threesome and he suggested inviting me. That really turned me on but never actually happened. In another trip, the 4 of us (3 guys and 1 girl) drank a little bit too much and started talking about sex and the size of our dicks, it even came to a point where we were willing to show our dicks but my best friend was shy and didn’t want so it killed the mood.

Now I’m think about inviting my best friend, his Gf, and the girl I’m in a “situationship” with to spend a weekend in my house again and try to make that work. I thought about having some games like strip or drink to kinda get in the mood but don’t know how they would feel about that. Also I don’t know if I should invite my other friend, I don’t want to leave him out because he is really close to me but I don’t think he would fit.

Can you guys give me some advice about this please?!