Another vote for the 17-55. It's a great lens. Tack-sharp wide open, a useful range, and IS. It doesn't have the build quality of an L lens, but I wouldn't call it fragile by any means. It's still a pretty sturdy piece of kit. I had mine for a few years before moving to full frame and never had a problem with it (other than lens creep, but my 24-105 L does that). Took it backpacking, traveling all over, etc and it always worked great. I've heard good things about the 18-35, but I don't have any experience using it.
I've only shot a couple of weddings, so I'm by no means an expert. That being said, if I was to pick two primes for a wedding reception, I'd want something at 35mm and 85mm. So on a crop body you'd be looking around 24mm and 50mm. But really, even with a second body, you're going to miss moments that you wouldn't if you had a zoom in that range. A 17-55 and either your 85mm f1.8 or 100mm L would be a pretty nice kit for a wedding reception. The macro's abilities to get close-ups of the wedding rings, flowers, and place settings would come in handy. But the extra stop of light in dark reception halls would be an advantage of the 85.