If you want to sell your wife on the idea that a pond is a good thing, you need to make it attractive...not just attractive to you as a fishkeeper, but also to her. The two best steps in this direction are simple.
First: plants. Flowers, foliage plants, aquatic plants...all of them. A water lily is what sold my wife on the pond. The first time a couple of leaves unfolded at the surface, she was hooked. And the first time that a bud opened and that lovely little flower burst into view, she fell in love. To this day, both she and I spend more time messing around with plants in and around the pond and it's very relaxing.
Second: fish you can actually see. Oscars are a favourite of mine, but like almost all aquarium fish they become practically invisible when viewed from above. So what's the point? You need colourful fish that are visible at a glance to a non-fishkeeper. Koi and goldfish are great, but they grow fast and will soon outgrow your pond. The quick, cheap and simple alternative is Rosy Red minnows, a colour morph of Fathead minnows. You can buy a bunch of them dirt cheap as feeders, they stay small, are very active and easily visible and they quickly grow tame and charge forward at chow time, creating a cool little feeding frenzy. They breed like mice, and eat easily available and inexpensive food. They present no difficulties and make for a really nice display in a small pond like yours.
I'm partial to them also because they are very hardy in my cold local temps, and even survive under the ice as long as the water doesn't freeze solid all the way down (which mine almost always does). In your climate, you could go with Medakas (Ricefish), mollies, swordtails and platies, probably many other small fish bred for colour. Whatever you do, don't select true tropicals that require a heater; the electric bill to heat an outdoor pond will be insane.
