To my way of thinking, you really really want lights on a ride-it-every-day kind of bike. Riding around in the dark minus lights is no fun at all. I've done enough of it, thank you very much. So when we got the Mundo, on went a dynamo hub(Shimano DH-3D30) and a set of dynamo lights; a B&M IQ Cyo N plus headlight and a Topline plus rear. The headlight's good; I can see and be seen at night. It's not a bike I ride every day, so not having to think about batteries is good. I don't know much about the rear light; it's hard to see when you're riding.
The standlight (where the light stays on while stationary) is a good thing. You can pay extra for a senor that will turn the light on when it gets dark. I didn't bother; I just leave the light on all the time. LEDs last for ages, so why not? Cabling was easy peasy. B&M provided a cable with the light. Naturally, it was to fit a standard bike, so I had to dig up some figure-8 speaker cable, make a quick trip to Jaycar for some spade connectors and find some heatshrink tubing. There was one little issue, which was that the rear light connectors on the Cyo where just little blades on the ends of short lengths of wire. The connectors bumped together and shorted out until I put heatshrink over the plugs.
Oh, and the bolts on the rear light were too short to fit through the rack on the Mundo. I bought some metal plates with holes drilled in them from the hardware store and that fixed that.
It's early days, but cargo bikes and dyno lights are a good fit. I really can't notice the drag, particular with the kids on the bike, and I really really like the always-there thing.
We got the lights and hub from Starbike; about $200AUD all up. I did the build myself and re-used the original front wheel.