Without knowing more about your data I'm not sure about your table structure, but I will say that GUIDs/uniqueidentifiers are controversial for clustered indexes. Traditional logic says that your clustered index should be unique, small, and sequential. GUIDs are unique, large, and random. (There is a newsequentialID() function that you could use as a default value to get around the random bit, however.)
An article against random GUIDs as PK/clustering keys: http://www.sqlskills.com/blogs/kimberly/guids-as-primary-keys-andor-the-clustering-key/ Summary: Your data can end up a scrambled mess, and selects of ranges that should be next to each other can be slowed down. Also, it takes up too much space in large tables and indexes.
An article for random GUIDs as PK/clustering keys: http://blog.kejser.org/2011/10/05/boosting-insert-speed-by-generating-scalable-keys/ Summary: If you have a LOT of inserts, it might be faster to spread them out instead of having them all be "at the end."
Personally, I think that if you have a specific business/logic reason to use GUIDs, then use them. Otherwise, you might want to consider using an autonumber column instead.