You don't say how big the pond is. As we're getting towards winter, fish eat less with dropping temperatures. The advice we go by is not to feed at all if your pond water is below 6C as the fish can't digest food even if they take it. We have mixed koi carp and goldfish (although I can't tell the difference!) and in summer we feed the Koi pond pellets, and in the winter they get wheatgerm mini pellets (easier to digest). In the summer with long days we feed them up to 5 times a day if they come asking, but as the days get shorter it goes down to once then not at all. Your fish are used to flakes so carry on with those then perhaps introduce something a bit bigger in the summer.
I would worry about your pond freezing solid, depending on where you are and the size of the pond. Our pond is about 2 1/2 feet deep with a surface area of about 150 sq ft and it has only once frozen solid, when loads of toads were frozen to death. Last winter half our fish died, but it was cold and the winter was longer than usual almost everywhere. Also we were unable to keep a hole open for oxygen exchange and we felt a pump would just bring warmer water to the top so freeze faster.
I wouldn't agonise over exactly how much to feed your fish, rather work out how you are going to protect them in winter. There is plenty of info online and in books. You could even get a large indoor cold water tank for them over winter - that may be safest.