S.H.
Anytime and per circumstances... a child needs to go to Daycare. It can't be helped. In an ideal world... you can send them to daycare when you want. But this is not your situation.
Your Mom, has thankfully, said her feelings. It has to be respected. I personally know a lot of the Grandparents at my daughter's school... and they complain about how they just can't take it anymore... and even just driving back and forth to the school tires them out immensely... BUT, that their Mom/Dad RELIES on them... BUT, they get NO vacation even when the schools & the kids have vacation. One Grandparent sarcastically joked that "even if the parents has a vacation themselves they STILL bring the kids to my house to baby-sit... I get NO break. And I have to cancel my own appointments and socials..." AND they also commonly complain that they get NO appreciation for their sacrifices....SURE they LOVE their Grandkids...but that does not make them the default baby-sitter for anything and everything. One Grandpa I know says he spends ALL his day taking his Grandkids to and from school (they are different ages), and have to talk to the Teachers for the Parents, check with the school about events and ask questions too... JUST like a Parent...but they are not the Parent.
Using a Grandparent to save money is common.... but, it has to be fair. If a Grandparent is expressing exhaustion and/or that she get days off-- you NEED to do that. What if she gets sick? Hurt? Ill? Does it feel good knowing that she can't even go to her own Doctor or Dental appointments... that she can't even go out with her friends for extended luncheons, that she can't even take a nap? THIS is what the Grandparents complain about, that I know.
One Grandma told me that not once, did her kids tell her 'thank you' for babysitting EVERY DAY INCLUDING WEEKENDS. PLUS, she takes the kids to all their weekend extracurricular lessons and games too. Meanwhile, the parents just have a 'break' all weekend. And, a lot of Grandparents have a hard time saying 'no' so they just go along with it or they feel bad for their Grandkids.
Not saying this is you... but I really identify with the elderly and Grandparents... after seeing what my Dad went through when he was sick and then died. I did not have children yet at that time... but I saw with my own eyes, what the elderly & my Dad's friends did.... babysitting STILL even if they themselves are old/tired/fatigued/or sick themselves. My Parent's friends, all Grandparents, go through this too...
Respect your Mom's wishes... she probably had to really think about it hard and it was probably very hard for her to even ask for a day off. It shouldn't be so. Grandparents and elderly can't be taken for granted... for our babysitting.
Sorry for coming off so strongly about this... but I have Grandparents that are friends of mine...and they tell me all of this. But they "can't" tell their grown kids about it... because it is such a touchy subject, or their kids will not understand.
All the best,
Susan