Get one of those little pill boxes that have the days on it and fill them with a pre-determined amount of food. That takes all the thinking out of it. Pop the lid and dump the food. Water changes...that's another issue. I'd get a small sponge filter and get the tank cycled. That way by Christmas if will be good to go and you might be able to get away with not doing a water change in those 3 weeks. Might be pushing it...if you could find someone that could do at least one or two for you then it would be good. Maybe get some plants...even something like Hornwort will really help soak up nitrates in the water prolonging the time between water changes.