Zoom setting for bounce flash
Whatever setting you like assuming the ceiling isn't as high as a church. The light emitted ought to be controlled by lens ADI (assuming your lens supports this and your camera has been set-up correctly), so the distance is calculated and the appropriate light will be produced, though that said, ADI only works when the flash is forward facing and not at a tilt as TTL metering will be used instead.
Take some test shots, though personally I set my camera manually to ISO: 100, WB: Flash, A-Mode (about F/6.3 depending on what DoF I want and distance to subject), though experiment to find what works best for you (I wouldn't set anything to AUTO mode though).
Mark @ Sonolta * Photography