Would you let someone take your child in a vehicle that you knew wasn’t well maintained?

I didn’t think much of it before meeting my SO, but he has his training in mechanics and that makes him super particular about vehicle safety because he knows what can happen if things aren’t maintained well. We have family members that want to take our daughter in their vehicles, but he isn’t comfortable with this because of a few reasons. First of all it’s winter where I live, it snows heavily here and they don’t put winter tires on their vehicles. They’ve actually admitted their tires are bald and they’re “all over the road” because of it. It’s silly too because they both have good jobs and could just go buy some so I’m not sure why they’re risking theirs and their kids lives by not getting some. They also don’t do maintenance on important parts like their breaks. My SO serviced their breaks for them last year and said he had never seen breaks in such bad condition. Tehy had waited years to service them. They had driven them until the break pads were completely gone and were starting to mold and warp into the other parts that hold everything together (sorry I suck at explaining what he relays to me lol). He said he was surprised they hadn’t failed on them yet. I feel kind of ridiculous saying you can’t drive with our kids but at the same time according to him the way they keep their vehicle makes it not road safe at all and I would never forgive myself if something were to happen.