You may disagree that that is the right path to take for personal reasons and that's fine, but an average middle class person who doesn't have kids has likely saved more carbon emissions than any other realistic action (eg. not flying, vegetarian/vegan diet, using paper straws). Don't discredit that.
None of that is going to solve the problem anyway.
I’d say most childless adults I know are way more carbon intensive the me simply because they can do more.
Kids are actually economical. They’re light, don’t eat much, can be entertained by pretty simple means and because they constantly grow and everything needs to be changed over, second hand goods are so accessible, nearly everything we buy for them is secondhand, bikes, skateboards, clothes.
I honestly ride my bike with my kids everywhere and we have not used the aircon once this summer. I’d say my kid uses 1/20th the emissions of an average adult with no children.
What if we focus on having a positive impact ourselves ? What if we teach our children what we're learning so that the next gen might eventually do things better than we do instead of just saying "oh yeah kids are just bad for the environment, but I do literally 0 efforts myself to do something, so here's a nice excuse I made up to justify my behavior". Sort of.