I can appreciate your topic. My wife and I are creeping up on 50, so I think/hope I fall in the middle somewhere. LOL We did have children late in life, and have twin 10 year old boys.
We've struggled with making friends in our day to day life, and much more for camping friends. We've got one family that we've done things with about once a month for the last 10 years. Outside of that, everyone in my life is just an aquantence that I have to talk to early enough to get on their calendar. Even then, they'll only see us if nothing better comes up.
I think this is a comment on modern society as a whole. Technology has taken us all further apart, not closer. I have a few hundred people that will hit "like" when I post a camping picture, but none that will actually come along.
Now, before you go thinking I'm hard to get along with and the problem, you must know that my wife is very sweet and this phenomenon still happens to us! ;)
We have had camping friends come along as guests a couple of times, and I was left feeling like a "host", not a camping buddy. Expenses went up, the amount of work went up...my time relaxing in a lawn chair went down.
Where to find friends that have their own camper and kids that match us? That's a tough one? I will say, our boys have made friends on almost every trip. Within minutes. If I can take any clue from how they do it, you must stand in front of someone's camp site and stare at them until they come over and say hi. Last time I did that, the camp host asked us to leave. Hahaha.