We went with 9 friends and from start to finish loved every minute of the 6 day Grand Canyon rafting trip. Guides were truly amazing - for both river knowledge and as human beings. Food was very tasty and included eggs and bacon breakfasts, shrimp cocktail and a steak dinner. A week after returning home I still awake each morning wishing I were back on the trip with my camp-mates. I wouldn't do anything differently and highly suggest you book for a trip whose memories will last a lifetime.
I'd like to point out that in addition to the beauty of the trip another awesome feature was lack of cell phone connectivity. This provided 6 days of disconnecting and bonding on a river trip where you rarely ever see a man-made structure. So the river trip is much the same as if you did this 50 years ago. Can't get this kind of bonding experience many places anymore.