The chances that your GF will want kids will escalate over time. At 22, my GF (future wife) didn't think she'd want children. She turns 27 this month and we have #2 and #3 on the way. She's and incredible mom by any measure -- I've been very impressed.
And there's plenty of good news. Your GF can learn the basics by working with your kids and watching you, so she'll have a head start on dealing with her own. Between you already knowing the ropes and her getting a glimpse of the future, a second round of children often goes much more smoothly than the first.
totally true...things run incredibly smooth with our younger two because its our "do-over" family
shitty but there it is...I already knew where I fucked up with the first two...and how not to be a selfish ass with the younger two
also (not that this would be a prob for woot) but with my first two I didn't have enough money to do a lot of things right/the way things should go
second go around I know what things cost and whats worth paying for and whats not
didn't stop me from buying that fucking stroller I've used three times tho...god dammit