I'm not sure how comfortable I am with this, but I concur with John. No offense to Joe Bentham (who I gather IS a caddie up there) but after my first trip I have never taken a caddie since, and have never had any regrets. Oh, I won't go far as JK does in his inimitable style as to say "there is not a quirk on the property" - I found plenty of quirk. But I also never felt I needed a caddie anywhere. One certainly can get around just fine - I know I did. And yes, piggybacking off of someone else's caddie is very fair, so long as you do throw in a few bucks at the end, as John says.
If you have to have a caddie for whatever reason, I can't see the worth of taking more than one per group. The push/pull carts do work darn well.
TH