There is no 1 correct answer, it looks different from all of them. Personally I prefer the North Rim but thats just my subjective view ridiculously coloured by the fact I dislike crowds out?
http://www.hatchriverexpeditions.com/trips.htm
They finely have a 4 day trip with poorly hike out and hike in options
For the Grand Canyon
http://www.westernriver.com/trips
Bryce is a little dry for raft trips
First you might want to consider a side trip to Moab and a trip along the Green or Colorado Rivers in the Canyonlands district.
The area is simply spectacular and usually a little less crowded than the Grand Canyon plus there are some super 4WD trails and great raft trips
http://www.utahoutventures.com/ratfing/
cataractcanyontrips.htm