My friends do have functions both with and without kids, we also have "girl's nights" too and so do the guys. There is a time and a place for everything. It is up to the hostess and she is well aware of how her dog is. I do remember several times as a child where I was the only child present at adult functions. The hosts allowed me to attend because I was well-behaved. The reality was that I was raised to behave or else.
I remember several years ago where the company that I was working at the time would have an elaborate adult formal holiday party. I remember hearing that one person had a fit because he and his wife could not bring their daughter to the party and she would go everywhere with them. I think that the host was out of line and should arrange w/the ex if he wants to attend.
Another thing: Remember 10 years ago when they were trying to make Las Vegas a "family" vacation spot? Ten years later, it has failed and is back to being an adult get-away. As I said, there is a time and place for everything.
Life is all about a$$; you're either covering it, laughing it off, kicking it, kissing it, busting it, trying to get a piece of it, behaving like one, or you live with one.