I do think it ridiculous this practice of tipping anyone who comes into contact with the bags. I do it, but it is over the top. Exactly how much are these bellhops paid by Disney, because with these tips I'm sure they'll make more than I do (and I'm a professional). Incidentally, my best friend worked as a car valet driver at a hotel and seemed to be earning way in excess of me on a daily basis due to tipping.
I also have to say, if I experience poor service or rudeness (which I have had from some in the past) when they complain about the weight of bags etc then I feel very strongly that the tip gets docked seriously. I have no intention of being taken as a mug who has to tip regardless of the service just because I'm from out of country. Also, I absolutely find it enraging when a bellhop asks you to give them a hand with a bag/case; The answer, 'no, it's your job for which you are paid' springs to mind. I will agree a tip size with my family (I'm the youngest but probably the one given the responsibility most times for handling this stuff). Maybe I sound kind of harsh, but I feel very strongly that the tip is not a guaranteed thing until the customer experiences GOOD service, not just service.