I use the mini food processor to pulverize onions when I'm cooking for my son. He likes the flavor, but not the pieces. My daughter used dried chopped onions for the same reason. She says the kids never notice those. I'm not sure I could get enough onion flavor for me with onion powder, plus I prefer fresh.
For t he green peppers, I'd cook a little dish on the side to add to mine. Either you like green peppers or you don't.