It's hard to change people, but at least we can learn to handle our responses better.. I've been working on my responses too... Not that it has established clear boundaries, but everytime somebody tries to cross the line, I know it right away and respond much better now.
Btw, coming back to your mothers day question, would it work for you to meet them at a restaurant for a lunch or dinner... or maybe just do icecream or desserts...from 4-5 pm to celebrate mothers day with them. Your mom can have her time and you can have the rest of the day. Public spaces are easy to enter and leave, than personal homes.