Entitled parent/grandma

This last Tuesday was my mom’s birthday. I worked all day (6-4) and am 36 weeks pregnant. I made sure to go to her house with our other 3 children after I got done working to cook her supper and clean up the meal/ spend time with her. That day she had already started blowing up my phone about not getting to see the kids long and asking to switch vehicles with me so she could see her grandkids longer. I said okay and she took my vehicle to her home (w/ car seats). Then when I was done working I drove her vehicle there. For her “gift” we decided to offer to take her to a butterfly exhibit and lunch with the kids to make memories. When I told her about our plan she instantly said “well that sounds fun but I am definitely not going to do that anytime soon. It’s too hot for that. Maybe this fall”.

So I said sure and dropped the topic. Now today she is messaging/calling me because her and my sister made a plan to go swimming tomorrow @ my sisters boyfriends house. Personally my husband and I do not care for my sisters boyfriend and we also don’t enjoy swimming. We talked about going and decided we would pass because our kids can’t swim and typically enjoy playing in water they can touch/playing in the sand more than anything. When I told my mom our decision she got all upset about it and then tonight over the phone told me how her and my sister are mad that we won’t go and how they don’t get it. To the point I could hear my sister saying shit in the background but then when I said “what did she say” my sister got quiet and refused to answer. Conversation went completely silent and I just said “ok well have a good night” and hung up the phone. My mom messaged me then and said she wanted to do this with us all together for her birthday… then proceeded to say if we don’t want to go fine but she wants to take just our oldest child to have fun. I just feel like it’s guilt trip to get me to change my mind and my husband told me I’m being a push over/people pleaser if I go back on what I originally said. I am just so tired of feeling like I constantly have to make people happy and it’s like it’s never enough. Just looking for advice