Being honest is selfish

I just listened to Brooke’s live call and the relationship I have with my mom was very similar to another caller. It’s based upon me trying to please her and be a “good daughter.” What’s coming up for me is that if I just behave how I want to around my mom, that’s being selfish. I will likely hurt her. This also reminded me of how I feel about spending time with my brother and sis in law. I’m often walking on eggshells because I don’t want to upset her. My brother asked if we wanted to rent a house with them for a week and rather than saying I don’t want to spend a week walking on eggshells, I lied and said I can’t take off work. The reason I feel selfish is that my brother has kids and my kids would probably love a week with their cousins. I then start to feel like I’m the issue because I can’t handle her and in turn, I’m the cause of my kids not being able to spend the week with their cousins. I feel like I can’t be myself around certain people like my mom and sis in law and not sucking it up and dealing makes me feel like a selfish whiny bitch. (Sorry for the language)
What do I do?