I wouldnt worry in a year the koi will outsize the goldfish and shubunkins.. just make sure the koi are getting fed, you may have to hand feed if they will do it..

Fish are very curious and usually friendly creatures. There is a hyarchy among them also, I have noticed. There can be bullies that prevent smaller fish from eating, so you may have to watch for that, if introducing smaller fish. They'll soon grow and adjust. I wouldn't worry about it, as long as the other fish are not physical (pushing them or crowding against the walls of the pond - other than spawning).