If you had the temperature problems you think you had, leaving it on the cake isn't going to make it enough less of a banana bomb to matter. On the other hand, I've NEVER had a problem getting a wheat beer with a slowly floccing yeast to carb, with some of them being ready in as little as two or three days, though to be fair those beers were better 7 to 10 days into carbing. So if you used such a yeast, I suggest you split the diff and leave it on the cake one more week and bottle two weeks before the event. That'll be plenty of time for them to carb and at least give the cake a chance to clean up a bit of the banana.
If it were any other kind of yeast, I'd say bottle now to give it the maximum chance of carbing well in time.