I have five kids. They are pretty much all adults now. My oldest has always wanted lots of kids. She is now married and has two... and is now thinking that maybe she only wants three.
My second child (a son) has always wanted to be married and have lots of kids. He is now 22 and is enjoying being single and 'grown up' and although he still wants kids in the future, he's decided that waiting until he's at least 30 is probably what he wants.
My 3rd child doesn't want to bring any more kids into the world... probably. He has always thought he would adopt when the time comes. He's 21 and single at the moment as well, so regardless, it isn't on his radar yet.
My 4th child (daughter) is about to turn 20. She has been in a relationship with the same guy since she turned 15. She has never been interested in kids, having kids or even marriage. She thought she MIGHT want kids in her 30's... BUT the past 6 months has been crazy for her in that she suddenly feels this deep craving to have a baby. She is still on birth control and wants to be financially settled before that point, but she is always talking to me about how weird it feels to actually be interested in having kids. She never thought that would happen.
My youngest is 17 and wants kids... probably... someday.
We're a very close family and get together at least once a week. All of the kids are fairly close and love being a part of a big family.
As for me, I don't get the parents who feel like they NEED grandkids or whatever. I don't understand the pressure to have kids OR to NOT have kids. Having kids is a HUGE thing. I wanted kids for as long as I can remember. I babysat tons of kids, loved kids to death... but having my own was still a shockingly hard thing to handle. Raising kids is such a lifetime commitment that I am SO GLAD I did. I'm glad I had them when I was younger (had five kids from age 20-30) because now they're mostly grown and I'm not even 50 yet. I feel like I have all kinds of time and energy left to enjoy them as adults.
Anyway, this is turning into a post of it's own. I was trying to share that even kids from the same family have such various views... and then life happens and opinions and thoughts change. I think it is awesome that you're thinking this through and thinking about what you want (or don't want) and I wish you all the best.
Regardless of our plans in life, sometimes we get surprises, sometimes we don't get what we want, but it's all about the experience and the relationships as far as I'm concerned.
You're doing great!
(Also, I've been pregnant 6 times one miscarriage and 5 of those times I was on birth control of one sort or another, so I never really had the chance to "plan" for kids... they all just kind of surprised us when they were ready to be here, apparently!)