I think if you plan to feed them, it would be worth using a gravel cleaner to suction all the waste and fish poo off the bottom of the container.
If you're going without a filter, I think alternating between feeding and 50% water changes could work, goldfish can go up to a week without food, I've left my single tailed common without food when I've been away and she's been fine, but if you have fancy goldfish then I'd be wary because I'm not sure how they are affected when not fed, as they genetically have sensitive swim bladders that can be affected by food and such. Hopefully one of the other members who owns fancies can chime in with advice
