I'd also recommend a separate flash. The flashes built into the cameras are pretty anemic at best, are in the worst place possible for redeye and ugly shadows, and put a heavy drain on the camera's battery. The 430EX II is just one possibility, tho it's a good one. There are smaller and larger flashes. And there are some good, third party flashes that might do.
The 24-70 will give you a bit more options than just the 70-300... However, if people are telling you tales about the 24-70 Mark II version, take them with a grain of salt. It's not on the market yet, won't be generally available until next month, if memory serves. So very few people have actually seen or used it. Maybe they are refering to the first version of the lens, which is quite good too. Both are very pricey, though... the new model will be substantially more expensive than the current one.
The 24-70, current version, has a very large lens hood that will definitely cast a shadow if using the camera's built in flash. It remains fixed and the lens barrel extends inside it, when zoomed to the 24mm end. The new Mark II version isn't going to be much better in that respect, it's lens hood is less deep, but it isn't any smaller in diameter, and the hood bayonets onto so extends along with the lens barrel when it's zoomed to the 70mm end of the range. (Just the opposite of the current version.)
You might want to take a look at the EF-S 17-55/2.8 IS. It's wider and the gap between 55mm and 70mm is pretty meaningless. As an EF-S lens, it's specifically designed for a crop camera such as the 7D, a bit smaller and lighter, and a lot less expensive tho far from inexpensive.... It offers high image quality and good, solid, mid-grade build. It's not an "L" (no EF-S lens ever will be, by definition), but it's build quality is "USM/Gold Stripe", which is Canon's mid-grade. It also would give you a truly wide angle of view. Not super wide or ultra wide, but decently wide. 24mm is not very wide at all on a crop camera, it's sort of a "slightly wide normal", at best.
The 17-55/2.8's lens hood (sold separately, since it's not an L-series) also would possibly obstruct the built in flash, depending upon how closely you are focused. Most lenses in this range will see this problem with a built in flash (the 28-135 does, too, I know from experience). Removing the lens hood temporarily will help, but in some cases won't entirely prevent the partial obstruction. So, ultimately a separate flash is in many ways the better solution... especially if you move it further off the lens axis with a flash bracket and an off-camera shoe cord. It makes for much nicer lighting, whether direct or bounced (which gobbles up a lot of the flash's output).
I use a 24-70, but complement it with a much wider zoom (12-24mm Tokina, in my case). Still, I thing the 17-55mm is well worth a look. It also has IS (24-70 doesn't)... not a feature I feel is essential on a wide to short tele lens like this, but nice to have when you can get it.
The 50/1.8 is a "short telephoto/portrait" lens on a 7D. For your purposes, you might be better served with a Canon 28/1.8 or Sigma 30/1.4. Those are more "normal/standard" lenses on a crop camera. Not really wide, but not really telephoto either. The Canon 35/2 is another option, but a bit long for a normal/standard.
My "go to" lens for architectural interiors, on a crop camera, is my Tokina 12-24/4. That's for broader view of rooms and such. There is some distortion, with such a wide lens. If your purpose is more to record details, you might use a longer focal length, but may need the lens to be reasonably close focusing.
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