You can use three Bonus Bucks on a 6-day stay at any "publicly available" rate. There has been some debate about whether or not AAA rates are publicly available. The official Marriott lurker says no, but others say yes. You might change your rate to one that is clearly publicly available if that gives you some added comfort about using Bonus Bucks.
My own approach would be to turn them in at checkout. At that point, few people will take a lot of time to argue about them. They'll just post them, and you'll be on your way. You might get an argument about not having turned them in at check-in, but you can find some excuse for that (like "I couldn't find them when I was checking in but found them later.").
Bruce