Rosy red minnows are endearing, and they are perfect for someone who wants a carefree pond and doesn't want to worry about predators every hour of every day. They are inexpensive, but what's more is that predators will probably never be able to wipe them out, regardless of how badly predator-proofed any pond that houses them is. They can also survive harsh heat, cold, and low oxygen conditions.
Shubunkins? I'd advise against those and other long-finned ornamentals. They cannot cope with predation very well, and are somewhat less hardy than "common" goldfish.
Two goldfish could certainly live in a pond of that size. That isn't a small pond at all.
But I would personally recommend comets instead. They are fast, tough, and cheap enough to replace if predators finally catch up to them.
Goldfish and rosy red minnows can easily coexist, but remember that if you want a crystal clear pond, it is better to consider rosy red minnows and plants only. Minnows will munch on mosquito larvae and muck on the bottom without destroying plants, as a goldfish might.
Plants can keep the water clear of algae, so a pond isn't complete without plants of some sort, at least in my personal opinion.
