The Dynohub or other hub style dynamo may indeed spin too fast for proper output, but it can be limited if you build a voltage limiter into it. I will also agree with @Unterhousen that for what you are looking for the Sanyo, and there was another manufacturer with a similar design dynamo that rode on the tread of the tire, would be a better way to go. Here is one on Ebay Sanyo Dynamo going for $45.

With that said, I have a Sanyo dynamo that I only use infrequently. It creates more drag than I would like and I prefer to use a battery powered light. At the time, the late '70's, this was pretty good. Battery powered lights needed the batteries replaced often, rechargeable batteries weren't that good and the traditional bottle dynamo had issues with drag, alignment and wearing the side wall. And the DynaHub output was marginal. Very clever design though.

One more thing about riding on the tire tread, the Sanyo slipped when it got wet leaving you with no light, or intermittent light at the worst possible time.