Yes, you will need an adapter with the surly deck. Your other option would be the new XtraCycle Flight Deck version two which just came out. It has a cutout for the yepp.
I bought a Dummy back in October, and I didn't get enough riding in before winter hit. Can't wait for spring...my 5 yo loves riding the Dummy to school. I got him his very own bell that I mounted to the hooptie, and he constantly rings it and talks to everyone we ride by :)
My two girls (4/2 now, though 3/1 when I got the dummy last year) love it too. We go grocery shopping, to the park, and all sorts of places on it. There is a bell on the stoker bars for my oldest... like yours, it's ring ring ring all the way.