I'm going to leave my mom at home and meet my soon to be brother-in-law's family without her
Why do you have to exclude your mom?
My mom recently gave birth to my sibling. And I want to give them some time alone.
I understand that certain events are too hectic to account for everyone, but your mom doesn't deserve to be left out. She's the one who gave birth, so she has every right to be with all events that happen with her baby. Not letting her participate is just cruel.
I think my mom just needs a lot of rest and her-time without the baby.
I see how your intentions are good, but family is family and I believe that she deserves to be with the rest of the family. Don't you want your mom to have a good time and get to know them? You all could get along really well and make great memories!