The koi will soon outgrow your tank. You'd need 100 gallons for each koi at the very minimum and more as they grow. Banded High fin Sharks also grow to 3 feet and are not suitable for tanks no matter what the pet stores say.
Why not find a place for the koi (an outdoor pond), decide what you're going to do with the goldies, and go from there? Are these fancies?
It's not a good idea to mix different types of goldfish too much (single tailed [comets/shubunkins] vs. split tailed [fantails/veils] vs. special needs [celestials/lionheads/telescopes]) the slower ones cannot compete in the long run. Two of my pond fish are spawn from a comet/oranda cross, because the pond they came from had a huge oranda mixed in with the comets, but I wouldn't do it myself because the average oranda would be seriously outcompeted by a zippy comet.
Your best bet is to decide what you're going to do with the fish you have and do some research on your own to decide what you'd like to do with that nice big tank. Once you take all the koi and goldfish out, you're playing with essentially an empty tank.