Rehearsal Dinner, who to invite?

So as of now, our rehearsal dinner is 57 people: which it includes: 8 grandparents (both sides) 5 parents ( my parents, his parents and step parent) the 18 bridesmaids & groomsmen, the 4 significant others to them, the 4 ushers & 1 significant other, the 1 reader & his significant other, (the other reader is a bridesmaid), the 2 gift bringers (Catholic wedding), the 2 ring bearers & their family( 5) , and then the priest ( but he won’t come).


My fiancé and I want to cut it down even more. We are wondering is it rude to not invite the grandparents since they are all extremely not well health wise & we feel like it’s a lot on them to go all the different spots. Just fyi: the grandparents won’t have to walk down the aisle. They have to sit in their pew and that’s it.
Or do we stick with 57 people? Since you can’t cut anyone else beside them since everyone else is doing something during the ceremony.