I feel like my mil is too much, instead of asking to take my son somewhere she just tells me and leaves!

For example for my sons birthday i planned to take him to breakfast, toys r us and other places. On his birthday he wakes up and goes out to hang with his grandma before she goes to work, next thing i know i get a text(below). It irritated me because she didn't bother to ask if we had plans she just took it upon herself to take my son and leave! Yesterday i told her we are going out of town on monday; couple minutes ago i get a message saying she gonna take him bowling and what not, not even asking me just telling me!

I try not to start an argument or anything because i feel she is grandma so its fine, but sometimes i feel she takes advantage of it! I say something every once in awhile but it doesn't seem to sink in!