I basically have a main cast of seven in my UF series.
One guy (Ryan) has an adult son (over 30), who isn't a part of the series, because he's rejected his dad outright, and is busy with his own family. Ryan, however, has basically adopted the MC of the series, which makes everyone happy, and the adult son is basically only brought up in comparison.
The MC (Stef)...given how a) immature b) crazy c) afraid of people d) incapable of trust e) asexual f) disgusted by anything to do with sex she is, it's rather unlikely she'll be considering kids in the near future.
Another character (Jones) has taken the job of being parental proxy to a kid in their care (Merlin).
Curt is the father of a three-year-old girl, who only exists because he was stupid and got his girlfriend pregnant after the formal (prom).
The last two character (Taylor and Magnolia), whilst not in a relationship as yet...will quite possibly get together and have a kid, which will be a major shift in their dynamic, though not a change that will change the tone of the series, just be a natural addition to it.
I don't think having kids in a story necessary detracts from it, or will make people think of it in a different way - some people have kids, it's a fact of life.
The only thing about kids that bothers me is when people think that they are a must, that children are the natural result of a relationship. Some people are childfree, some people want to focus on their careers first, some people may not necessarily want to pass on certain genetic traits, and some people would much prefer the relative ease of raising puppies. ^_^