Because the DS is under 7m, you really aren't required to mount any lights under the navigation rules (unless you are motoring). If you do, there are convenient sets of navigation lights that are sold for Kayakers. Get the LED version and find a way to mount them at the bow and stern. That's what I do.
You might need a strong flashlight if you have to pick your way through rocks, pilings, unlit docks or moorings...
Night sailing has it's own attractions, although it makes some people nervous. Beating against current into a rising wind as night falls is probably not the best starting point. Moderate winds, a good full moon, and the lights from a well-populated lake shore can ease the transition.
A UPS might have made a nice difference on my return leg, because it was nearly all close reach. On the way out, it was more like a broad reach turning into downwind as the evening progressed, and I flew a regular spinnaker. I find that in moderate winds, singlehanding a spinnaker isn't rocket science, even had a hand free to take some pictures.
~ greeen ~ lake ~ ~