How do I avoid sending my kids to Camp MiMi?

My MIL has been probing at having our kids over for an extended period, without us of course, for “Camp MiMi” since our first child was born. My FIL also probes about Camp MiMi.

My MIL has crossed boundaries since the birth of our first child. From feeding to mundane things, she crosses those boundaries. She comes from the mindset of “back in my day…” or “I raised 5 kids and they turned out great!” And she gets mega defensive if you disagree with her or what she thinks is best. It’s almost like a hit to her pride if I do things differently.

For example, she questions things like how long to rear face a child in a car seat, since they did it differently back when she was a parent. If it’s one thing I don’t play with, it’s safety. Until my kids max out weight, height, or head space on their car seats, they will be rear facing. That’s a battle for the future, though.

The biggest complaint is that I will specifically say NO to something and she will do it anyways or behind my back if she thinks she knows better. That’s why I don’t trust her. Point blank period.

There will get a point where she will directly ask, “when can the kids come to Camp MiMi?” I plan on using the “my mama heart can’t take it” excuse. I do not ever want to tell her the real reasons why I don’t want our kids staying over there. That is a recipe for disaster. A can of worms I never want to open. My husband is supportive of me and will speak up when he needs to.

If you have used the “my mama heart can’t take being away from my kids” excuse, did it work? How long can I keep that up? Any and all advice is welcome