Borrowing our hybrid !!

OP, you just answered your own question. IMHO, this is one of those times you remind your DW about the past history and be prepared to take a stand. Normally, I'm a strong supporter of compromise, but there is documentation here to support your position. Unless your DW is prepared to retrieve a dirty camper herself, fix or pay to have fixed all the broken stuff and have it ready for your next trip....... Absolutely not. You and the DW need a serious discussion on this and I think you need to remind these "kids" of the reasons why you will not loan it again. Right now, they are being enabled and their irresponsible behavior is being condoned. Good luck.