Like so many things in the hobby, feeding is not an absolute. There is a fear of over feeding that may have taken too much root, as not long ago I read the #1 mistake of new fishkeepers is under feeding. Having 'said' that, fish always appear to be hungry, especially when you get near the tank (Pavolfs dogs). They are programmed to eat whenever food is available, whether they need the nutrition or not. The more you feed them, the more they will eat...and the more they will poop.
Whether it's once or twice a day, feed no more than is consumed in 2-3 minutes. If you have a fair amount of surface turbulence from filters and such, you may wish to turn these off during feeding.
I typically feed twice a day in small amounts except for fry that are fed about 4 times a day. My main tank currently has a dozen or so Juvenal's so I'm feed two - three times a day.
I don't have much experience with weekend feeders. On a 3-4 day trip last summer, I added one of the newer Tetra gel w/e feeders. When I came home, they were pretty much intact - I don't think the fish touched them. The underside was covered with snails, so I guess they liked it.
I'm also Leary of the mechanical feeder contraptions. I had one once long ago for Abbey's goldfish. It tested fine, then failed when we were away. Fortunately fish can go for long periods w/o food (less so for growing fish as previously mentioned).
If you're planning a trip lasting more than a week, you'll need someone to come in and feed...but it doesn't have to be every day and you might want to carefully instruct (or pre-package) for specific amounts to be fed.