What is this whole thing of if you don't

Baptize your child they will not be able to get married in a church (i'm talking about Catholics) my husband's mom and everyone on her side is Catholic while his dad is Christian. Anyways, her family has been asking us when are we going to baptize our daughter at first I said I would when she's a year but now that I think about it I don't see a point I mean the only reason why I said yes is because If my daughter ever wants to get married in a church I don't want her to be mad at me for not baptizing her other than that, like I said I see no point in it my husband and I aren't religious. Is this rule applied in every religion ? The whole "if you're not baptized you can't get married in a church". Isn't there something you can do instead like pay extra money to get married in the church? Also, a big reason why i'm saying no is because my MIL is telling my husband to let his sister be the god mother and I don't like her at all and as far as I know the god parents are the ones who look after your child if something happens to their parents so there is no way in hell that I would ever allow that