Actually, in our experience FP+ does not even guarantee you a seat, it only guarantees that you will be allowed in the theatre even if you have to stand. We did this in October without FP+. About 15 minutes before the show, they let the FP+ line in, immediately followed by the standby line. Being standby, we got center seats in the front row of the back bleachers which we liked. I think I preferred that to some of the far side seats down front the FP+ people got (this was back when front and center was reserved for the frozen premium package people- isn't that over now?). After the lines were let in, FP+ people continued to show up. The theatre filled, and after that they continued to let people in who had FP+, but those people had to stand up down the side of the theatre for the whole 20 minute show. We saw a few who definitely were not happy about that since they had blown a FP+ on it. So the moral is that if you do FP+ it, you still need to be there 20 minutes early. As far as your BIL, whether FP+ is necessary depends on where you want to sit, and whether you want to take the risk of having to return for a later show if the one you originally tried to go to fills up. The standby people generally will be sitting towards the back. We were fine with that, but if you want a close up front seat, you should do FP+ and get there early.