Blanket statement much?
The amazing thing about humans is the amount of variation within our species. Not only are we adapted to eating a multitude of different types of foods, but we different types of foods (and at different times) affect different people in different ways. In fact, I was just reading a really interesting study wherein some individuals' blood sugar was affected by one food in a dramatic way, whist others were completely unaffected.
Disney Fantasy, you offer some really great advice, but you are always so adamant about this (along with your beliefs about cruising with a veranda in Alaska) and it can really stress people out if they don't have them (early dining and verandahs) and I just don't want to see anyone be caused undue stress as they plan their vacation.
Original poster, whichever dining you get isn't going to ruin your health or your vacation over the course of oneweek. Do what's best for your family.
And for what it's worth, on our last cruise in the caribbean, we remained on central time quite effectively and thoroughly enjoyed our late seating - sun position be damned. For Alaska, we also plan to have late dining, even though we'll be going the other way time-zone wise. We just like the flow of our day with late dining.