Just going to throw this out there...
I'm 23 and I don't like to go out to clubs. I feel awkward and know I don't belong, but I'm invited and I don't want to seem rude. I've realized I much prefer to sit at home with a few friends and have a Skip-Bo night, movie night, etc. Do I enjoy my alcohol? Well a bit...but I wait until the weekend to let my frustrations vent. When I have land, I won't be drinking at all...My time will be spent gardening, feeding, grooming, etc. I can't wait!
I don't have children so I'm out of that loop. I understand those with children always have prior commitments (welfare of the children come first!) and I don't plan on having them for at least another 3 years. Maybe your younger friends are feeling a rift because they don't know when you are available or you aren't stating enough that you don't like to go out and party?