Advice please?🥲

Every time I get together with my husbands family his 2 sisters always ask to be the one to change my baby’s diaper and I say no thank you, I got it. And they get offended or upset that I say no? I just feel that if I or my husband are not doing anything, then we should be the ones who change her diaper. They are both in their 40’s so they aren’t teens or anything like that, not sure if that is relevant but I’m just tired of always being the “bad guy” to his family bc I say no to some things that they want to do with my baby. Is it rude of me to say no to them to changing her diaper? I just feel most comfortable if me or my husband do it, it’s nothing weird or personal it’s just my preference and how I feel. Just don’t get why they think I’m rude for saying no 😭