It sounds like it could be a fun time. You always have to be wary of an uncomfortable situation arising, but it sounds like that will depend mostly on them. Will she suddenly become jealous seeing when you all get naked? Will he become more interested in you... beyond a sexual standpoint?

Things need to be discussed if you want to go for it. Bring up any and all potentially bad scenarios and discuss them up front. Make sure any rules are laid out ahead of time too. What are the boundaries? Who can stick or lick who and where?

I've had 3-somes and 4-somes and they've been good experiences. But I've heard from some peeps with not so good times as well.

If you think it sounds good... go for it!

__________________
Put me on wheels and I'll turn tricks.

Clever? Nah, I ran out of that years ago. But if you find this, let me know, k?
"The road goes ever on..." ~ Tolkien

In memory of my friend skip...
Go then, there are other worlds than these