Need Backpac

I have had a LowePro backpack for several years and have "mostly" been happy with it.  The biggest complaint from me is in regards to accessing the gear quickly.  I have to take off the pack to get to the camera.  My pack does not have the side access, so I have been considering a pack with that feature.  I also have a messenger bag type which allows for easy access, but would not have worked on the family hike last weekend because there was not way to carry any "extra" stuff for the kids.