on that body, if I were to have only two bodies, I would want something that goes wider than 24mm. There are some very different ways to go:
- Limited range, fixed aperture, fairly fast (f/2.8). Lots of options in the 17-50 range, or thereabouts, including lenses from Canon, Tamron, and Sigma. A very well regarded inexpensive lens is the Tamron 17-50 non-VC. Search posts here, and you will find lots of comparisons.
- Longer range, not fixed aperture, slower. The winner here, in my opinion, is the Canon 15-85, but it is fairly pricey.
If you are going to be indoors, the latter is quite slow. (I own it, and I love it for outdoors work).
One hard part of this choice is that while 17-50 is good for tight indoor shots and is nice for wide-angle outdoors, it does not include the classic portrait lengths. I use the 15-85 outdoors but do most of my flash shots of people with a Tamron 28-75 / 2.8. For candids, I think the best indoor setup is often a lens in that range with bounced flash and a bounce card, like a Demb Flip-It.
This is not what you posted about, but an unsolicited suggestion: do you really need 2.8 on your 70-200? It roughly doubles both the price and the weight. It is also a hugely expensive lens for someone starting out. If you don't really need that extra stop, the f/4 IS is a wonderful lens.