Depending on your Nutritional intake - yes they can help, though you will still get nailed by Doms - delayed onset of muscle soreness... nutrients cant counter Muscle soreness unless your cutting it with Morphine.
More importantantly is that you have both complex carbs and protein before kiting. Taking into account that your body is very slow to push that steak you had 2 days ago through to your Bowels - Im sure your not gonna run dry in the amino acid pool stores unless your anorexic.
Rehydration is more important after a 2-3 hour session of hard kiting to re-balance your electrolyte levels - if ones low, the body auto drops the others for equilibrium.
not many sports you go 2-3 hours without having a drink..
Remember Supplements as the name suggests - is to supplement "Not replace" your normal meals