I said maybe, only because I would trust my dad, but not anyone else in my family, and none of my friends. My mom overfeeds everything, and while that doesn't do anything to the goldfish but make it so they need to be cleaned more often, it would totally kill my bettas due to constipation.
When I do go out of town, I leave a very detailed care sheet for each animal individually, with exactly how many pellets they can have, what the tank temp needs to be, how to do a water change if needed, potential dangers, etc.