I definitely agree to twice a day. I work 3, 12 hrs shifts in a row 3 days a week and on those days I can only feed once. I feed in the morning and by the time I get home my lights are long off. I can tell a difference in my horses on Sunday. They are noticeably thinner from the 3 days of decreased feeding.
As far as dwarfs, I don't have them, so I can answer, but the auto feeder does not sound like a good idea.