Even though a camera is a high priority for me, I pack first then see how much weight I have and how much room I have left, then decide what camera to take.

Maybe you can pack an approximate load for this trip, then see whether you can still accommodate the slr, lenses, batteries, etc. I'm guessing you're looking at perhaps four pounds of photo gear? I'm not familiar with Canon stuff but their better lenses seem to be on the large side.

My tendency is to take an slr kit on shorter hikes and a compact on longer ones. The other benefit of a compact is I can keep it handy to shoot on the go. I don't like having an slr slung across my shoulder for long stretches, and when its in the pack I tend to not stop and shoot as often.

Cheers,

Rick

p.s. I find wide angle to be more important than telephoto, so I always make sure I have at least the wide end covered.