Don't forget that you also possibly have the options to change the time you go to Ogas or build a droid - my last trip to WDW I had a later Ogas reservation but went in much earlier as they had a really short line in the morning - they just removed my reservation (make sure to let them know if you do that so they can adjust). I've just walked into build a droid before, so it's also likely you could go at some other time if you talk to them about it... they also mentioned at Ogas that even if I showed up after my reservation, they wouldn't charge me a fee as long as I went in the same day, but if you show up later the line may be very long. Between being able to go in at some other time, and the two hour boarding group window you should be able to pretty easily cope.