Anonymous wrote:... the truth is that your kids won't hate you for saying no. Kids actually need structure and order, and you will be respected for maintaining it.
Bingo!
OP should be lucky that her MIL respects her and the fact that these are OP's kids and it's OP's rules. What I don't understand is whether MIL is sneaky one and does things that she has been EXPLICITLY told not to do with the kids etc. I make my own mother say to my son: Mommy does not allow you to do x,y,z when he asks for it.
For example, my mother has been well instructed that my son (age 3) is not to play with cell phones or watch animation movies unless I am there in person and decide to do so.
My in-laws and mother have also been specifically instructed not to give any cookies that I have not approved of. If they go behind my back and do it and I find out, I don't give them any grief for days. I just say that I am unhappy that my rules have not been followed and that this sort of things are not conducive to raising a child to be honest and respectful of his elders." And then I move on without further discussion.
But again, I am not afraid of being the bad cop!