I spent some $$$ a while back and purchased an Eheim dual chamber auto feeder for one of the issues you described. When I'm away, I don't want things to be too complex for whoever is looking after the system. I've read more than one horror story about well intentioned tank sitters overfeeding and the resulting disasters. I use the autofeeder on a daily basis, so when I'm away, there's no change in the routine except that the critters don't get their evening treat of thawed out frozen goodies.
I don't have a sump, so no overflow to worry about in that sense, although my skimmer is fed water from a pre-skimmer box which works in a similar fashion as an overflow, potentially skimming floating food before it has a chance to sink and be consumed by the intended critters. I never turn off any pumps or powerheads for feeding time, the fish have to chase the food and that seems to be working just fine, even with two VorTechs pushing plenty of water. If they're lazy, they go hungry. Once they're hungry enough, they chase down what they need. This doesn't work with all species however, so your mileage may vary.
I tried one of those feeding rings once I started using the Eheim auto feeder, but found it was too small and much of the food was dropping around the perimeter and being lost to the skimmer. The feeder's mounting options were not working for me, so I fashioned an acrylic hang on mount for it with a section that extends below the surface of the water. The extension does the same job as the floating feeding ring, but better in my situation. It captures all of the stuff dropping out of the feeder, allowing the flakes to soak a little while the granular stuff sinks straight away, but is immediately dispersed by the flow from the VorTechs.
Several photos of the rig follow:
It took several attempts to get the holder design right and I added a little ramp to give the feeder additional tilt. It wasn't dispersing large flakes too well in the horizontal position.
