For an absence of less than two weeks, the risks associated with dissolving block feeders is much greater than any imagined risk one can concoct about the fish going without food. A mechanical feeder lowers the risk, but many of these are not foolproof and they simply aren't necessary, unless you have fry or very sensitive fish.
Wetman is right; if you leave your fish without food, the water will be clear and of good quality, and your fish will look healthy and happy.
HTH,
Jim