Ah, we're weeks 16 and 17 and daughter's 17 and 18 and we each have weeks in November so we may find ourselves checking out as you're checking in as we're there week 48 right ahead of you.
As far as the car rentals go, like you've said, the smart thing is to get apples to apples quotes from all concerned and then go with your gut and don't look back.
And here's one more suggestion, isn't there also a fellow that rents through the Towers front desk to its guests? I'm thinking Winston and perhaps United Car Rentals. I don't know why this sounds familiar since we've never used him but I have seen him taking guests to the airports at the end of their stays. He seems like a really nice guy, too, but we've always liked getting our car at the airport and being done with it.
Check out the Towers timeshare site sometime when you or your social director has time to spare. It requires registration but that's not a bad thing as it seems to cut down on the spam. Of late, most people seem to be using it as a place to feel out rentals of their units and sometimes, as a place to test the waters for resales but you can even get the occasional up-date as to what's happening there, if anything.
Good luck with the car thing, whomever you use, and I wish you a great trip.