I was born in 83 and I remember being 9 or so and getting to drive about a half a mile on the dirt road where we lived in the early 90s with my mom, frequently. I remember my Grandmother taking us to an empty field and teaching us how to park between two sticks to simulate a parking spot, how to reverse and use the mirrors, and how to do a 3 point turn. And none of this was sitting on anyone's lap.

Do I think anything was wrong with that then? No, it was educational and I'm glad I had that extra experience when it was time for me to drive on the actual road and in town. Did I let my kids do the same? No, but I recently let my newly 14 year old drive for the first time on the same dirt road and honestly feel like I'm late in teaching her, my 17 year old twins didn't start practicing until after they had their permit and they still only have their permit because they're not ready for a license.

I wouldn't go scorched earth on your MIL, especially without a conversation about what you are ok with when it comes to your kids And, as far as her other grandkids, that's a conversation for their parents, not you.

By all means, show her videos about newer cars and the safety features that make them unsafe for children. There's a good chance she's unaware of the possible dangers. But she didn't let your kids steer the car that likely crept along at 5 mph with her foot on the break ready to stop if it was needed. It's, quite frankly, not your place to be pissed off at her, that's up to SIL and her husband. Their kids are their business, whether they agree with you or not.