(i haven't check the whole thread, so sorry if I'm doubling up here)
maybe a call to the insurance company you already have, see what their stance is, beyond that something in writing and his details (photo of truck and registration etc) to make sure you see the fender again!
maybe your policy had some allowance for towing? you might get the first 150km (or whatever) on insurance?
Don't do it on cash, get all the details correct, ABN etc and if it an option, you could ride back with him, and sleep in the fender when needed. Put the family on a nice aircon coach and come out smelling of roses, figuratively...

