I'd have them stop in 2-3 times a week, and I'd have pre-portioned foods like Orion mentioned. The most common situation in this instance is that whoever is taking care of the fish while you are away overfeeds the fish and causes illness/death. And you don't want to be overfeeding, especially when there'll be no maintenance on the tank. Or will there be?
Instead of using plastic bags to portion the food, though, you may want to try some of those cheapo 50 cent pill-a-day containers. When I've tried to use plastic with flake food, it all sticks (static) to the plastic and pretty much nothing comes out.
Or since food will be more scarce than usual, you may want to feed something more nutritious while you're gone, like frozen bloodworms. These can be precut into little pieces (or you can use the cubed kind) and that can be fed instead.
PS - Just don't use those "vacation feeder" tablets. They're pretty useless.