do not feed them heavy and do big water change day before!!! that is stupid. on many occasions i have had customers do that and lose loads of fish through it! by changing a large volume of water you are going to possibly change the water chemistry too much and you will not be able to anything about it while your away.
Honestly just do your normal thing, make sure all pumps and filters are ok don't touch the tank or add vacation feeders, they will be fine for loads more thena a week.... 8 days will be nothing to them!! may do them some good!! lol