Your only option is to get an electronic feeder. The "holiday" food blocks are more trouble than they are worth: they will pollute the water more than anything.
Why do you not use a timer for the lights? They usually only cost £2/€2/$3 or so. It is much better for the fish to have a set lighting time which is always the same.
you can put your light on a timer if you want but its not really neccessary if no one will be there.
Actually, I would say, that it is necessary: how would you feel if you were left in a dark room for a few weeks? Fish are still animals and should be given a good environment to live in.