I'm not sure what you mean by "how does it work practically?"
I don't have children of my own, and I don't spend time with anyone else's. There is nothing to try and make "work".
What do you do at family events or if you want to socialise or pop over to a relatives to catch up? Do you ignore their kids?
I don't "do" family events and never have. I don't visit relatives. The only friends I have who have kids of their own I meet in social settings where the kids aren't present, the pub mainly.
What happens when they grow up...are they suddenly acceptable to spend time with?
It's not a question of "acceptable". I don't like the company of children because I find them both boring and irritating at the same time. I wouldn't keep the company of adults I found boring and irritating, so why would I put up with children? If those children are not boring, irritating adults later in their lives, sure, why wouldn't I enjoy their company?
I'm well aware of the fact children are "people too", but so are all adults, and nobody finds it remotely strange when people decide to pick and choose which adults they will spend time with.