I suspect you will do most of your work with the Tamron 17-55 with the flash mounted. You might try dialing the flash back to be more of a fill flash, but, especially if you are un sure, when in doubt ETTL usually does a good job. My common mistake is to try to shoot everything at the widest aperture (f/2 or f/2.8). I end up losing many shots to the thin DOF. Most people do not recognize a thin DOF....but they know an OOF picture. I talked to a Pro I know a few years ago and he lived at f/5.6 with a flash for indoor events. In other words, focus less on style points and more on capturing the moment.

You may want to invest in a bracket to get your flash off the same axis as your lens (granted, I've maybe seen 1 wedding pro with this) and maybe a cheap Sto-fen Omni bounce. I have one, but I honestly prefer the white card you can pull up. But, I am always reminded when I go to weddings (2 weeks ago). Wedding Pros seem to live with Sto-fen's on their flash.

For the times when you can't use your flash, I'd have both the 50 f/1.8 and 85 f/1.8 handy. Also, I would try to mix things up. Some shots with flash and some, when ambient light allows, without.

Anyway, just a few random thoughts.