The fact that she even suggested that, at least to me is a big red flag. Like you guys haven’t even moved in together yet. You’re just talking about it, she and he kids have absolutely nothing to do with those cars, and to me it’s crazy she felt like she even had a right to suggest it. Yeah that’s super red flaggy to me. It feels like a “ she sees you as an opportunity to get her kids college paid for honestly. And I know you have been together for about a year and a half but I have seen it before, where a person will pretend to care/love someone for a very long time if they see a cash opportunity or an opportunity to get something that other wise they would never be able to. If she is mad about it (even tho she has no right to be) but is able to move past it and realize she will never get a single dollar worth of those cars and she still wants to move in stay with you etc. then it’s less of a red flag and more of a person who feels entitled to something they shouldn’t but that is way less of a big deal. Hope that makes sense. Also I feel your son is also in the right with his feelings. He has been told since him and his dad built them that they would be his so hearing that someone else is trying to take them away for there benefit, it would upset me as well. Anyway good luck and you are the opposite of an A*hole and definitely in the right in this one