You are expecting way too much of your friends. Some people you may remain close with, others may drift away. That's totally normal. I don't think you being married and/or kids would change that. I don't have kids, and have lived through many friendships where my friend became a mom. Some drifted, others we found a sweet spot where we both were able to stay in touch and in each other's lives through the years. I'm an "auntie" to some of their kids. It takes both putting in the effort and being flexible, but also, some friendships are just different than others. Some the connection it doesn't matter what is going on in your lives, some are more built on a certain place and time in your lives. It's fine. I agree with rainbow where she said you need to get comfortable letting go more often. It's like you are holding on with clenched fists, not leaving room for things to change. You have to be ok respecting change in people's lives.
As for what to do, do what you want. Do what you are going to own. Don't go and then hold it against them that it doesn't turn out like you want. Just be genuine! People can sniff out bs a mile away.