I basically agree with you, and I don't think asking
DCL to store it is the right answer! I just thought I'd see if anyone had a different answer or idea!
I think the crux of the matter is that mom will have just gone through a divorce and is literally moving all her worldly goods in a car. She's meeting the family (my friend) who is taking her on the cruise kind of as a consolation/celebration that the divorce is final and then mom is driving her car in caravan back to live with my friend. She doesn't live in Orlando (further south) and so everything important to her will be in her car when they cruise. If I understand correctly, it's just that there may be so many papers that it won't fit in the safe (legal size documents won't really fit) and they don't want them removed from the lockbox!