Honestly, the day is in honor of you, and I believe you should be able to spend it as you prefer. If that means not spending that day with your MIL, I think you should have the prerogative to do that. I think grandparents forget, a lot of the time, that they got to experience things on their own, and we need to as well.
Our families are 300 and 600 miles away. We don't get to see them often, so I get to spend Mother's Day as I like, and my husband is really good about recognizing it's a day for me (I try to do the same for him for Father's Day).
But, we also don't have the luxury of grandparents doting on our kids, wanting to have them spend a Saturday afternoon there so we can do yard work. Santa shopping with our kids was REALLY tough this year (we had to get really creative).
So, having family close by is a double edged sword in many regards, unfortunately. I, personally, have no problem telling either family how we like to do things to create our own memories and traditions, and my husband supports that. I wish you had as much support from yours.
You only have a few more years with your girls at home, I think it's safe to ask your husband to support you in creating some of your own family memories before they're off to college and out of the house with families of their own. If he's a mama's boy, though, it may be hard to get buy in.
Good luck.