Considering these two lenses.....

I currently am the owner of an XTI with two lenses (18-55 IS, 55-200 IS). We are going to have a wedding in our family, in laws side, and they are going very cheap and asked if I could do some light photography work. I am thinking of just picking up the 50mm 1.8 for some portrait stuff. What do you think of this?

Secondly I love to vacation once a year. I plan for my next big trip as soon as I get home from the last. We went to Yosemite National Park this summer and it as sad that I couldn't get more in my picture in certain parts of the park. So I started looking at the wide angle lenses. Of course I have been researching the 10-22 Canon, Sigma 10-20, and a Tamron. I like the price of the Sigma but am nervous in stepping outside of the canon family. If you were to buy a Sigma lens (if you think it is good for the money or do I jump and spend the extra on the canon) where do you buy your lenses from? We have a photography store close to my house but I feel they charge too much for the convience of having it local.

Help.

B&H, Adorama, and Amazon are all good vendors. don't worry about venturing outside of the Canon lenses. plenty of companies make good lenses.

As for your in laws wedding, don't buy a lens for it. Tell your in-laws you are happy to take pictures but that they should pay for your lens rental. Then go to a site like borrowlenses.com and rent a 70-200 2.8 IS. another good lens for a crop is the 17-55 IS but i dont know if you can rent it. the 24-70 is a great wedding lens but not really on a crop.

I agree with Cosmo, rent some glass for the event. EF-S 17-55 f/2.8 IS + EF 70-200 f/2.8L IS (or EF 70-200 f/4L IS, for that matter) and a good flash and you'll be set.

As far as UWA's are concerned, look at the best one... Tokina 11-16 f/2.8. It will put your existing glass to shame, but you won't need to upgrade it anytime soon. It will allow you to focus on upgrading other things as you see fit.