I agree with Jonathan. I'm an older native speaker, and I can't understand exactly what this means.

First of all, this is extremely dated language. If you like the song, you can certainly just listen to it for enjoyment. But if your goal is to use music to learn English, I would recommend that you find songs with lyrics that use language that is more modern. That said, I think you've got the right idea about the meaning of "the lad for my notion." And from the context, I would guess that His "row de dow dow" refers to how he speaks since we're told that it affects his listeners (hearers).