DM has no concept of danger and thinks nothing bad will ever happen to her. I often question how I survived my childhood with no physical injuries. Not a single broken bone or hospital visit...
There are (unconfirmed) rumours that she once gave my cousins 9 month old a sip of coke.
She lives localish to us and would have the kids DD6 and DD3 at the drop of the hat but I just don't trust her.. DH thinks I'm crazy as we could be off having a whale of the time but...
We use nursery for childcare.
I left DD3 for about 3 hours one morning as I had an adhoc work meeting and she put her in DS's forward facing booster seat for a non urgent car journey a mile away to collect something that could have waited. She "thought she was old enough to face forward now as she's big enough"
DD3 had a very minor scratch and I asked her to get some savlon and before i knew it she was applying some dodgy antibiotic cream to "take the redness away" 
Oh when One DD was born she shoved some honey in her mouth at a few days old (some batshit cultural custom) before I could stop her. She has no boundaries. She can't be stopped or reasoned with. I had to insist she covered up her 6ft deep pond after she persisted with the fact I had never drowned in it as being a good enough reason to leave it.
My children need protecting from her. AIBU? I suspect not but DH thinks I am OTT!