If you decide to have kids, you'll have to make sacrifices. And that's fine.
Whatever you do, it comes with a cost and an opportunity cost. You only have that much time and energy. Does this mean you'll have to give up your career and public speaking? Definitely not. Maybe you'll force yourself to find - as Ben said - better speaking engagements. Maybe you'll force yourself to work not harder, but smarter.
If a career means to you - I don't judge or even imply - working 50-60+ hours a week, then yes, you'll have to give that up if you want to raise kids.
Of course, there are parents, who barely see their kids, but I think if you have the choice, it's better to be part of their lives and let them be a significant part of your life. Hence I use the expression raising kids. In my view, there is a big difference between having kids and raising them.
You can also consider another aspect. You'll work for decades. For long decades. You'll still have plenty of time to speak even more and work even more than you'd ever want. While having kids in older ages is a possibility, but it has both some dangers and probably more cons than pros. (I speak only of personal experience.)
I don't think you'd be perceived less seriously with kids unless you'd be the dad/mom who does nothing but shows his/her phone around the office with their little ones all day long. :)
While being a parent is a difficult job, more difficult than writing code or speaking in front of hundreds of people - at least to me -, I didn't regret and I can only encourage people not to hesitate and not to be afraid if you ever want a family. But that's something you should know!
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