I'm going to say that having children is a non-negotiable for me
That seems very drastic. Why would you say that having kids is non-negotiable?
I need to be sure I don't get trapped into this relationship.
Sounds to me you actually want kids but are just saying you don't to avoid being "trapped". This could cause problems because in the future you could end up married to someone who actually doesn't want any kids.
I don't care if we have a baby or not. We have to be honest about our lives and if she doesn't want children then it'll definitely lead to problems in the future.
Then I do not think that you having kids is "non-negotiable" is something that would also definitely cause problems. If you really love someone, you should talk about what they want and how they want to plan for kids, so that you will be both in agreement. You being unable to talk with regarding this matter may be very hard for your partner.