I like the good ol' "Dooku tosses a thing at Obi-Wan and Anakin" approach. Yoda shows up and nearly bests Dooku through ESB-type Force use, but loses due to his friends being put in danger. The joy inherit in the Yoda vs. Dooku saber duel is how bombastic it is. Like the youngling murder scene in Ep3, it's gotta be the whole thing or nothing.

Even though I'll deny it if you ask, I keep continuity with the broader EU (or whatever it is called now) in mind. I think showing a very quick use of Yoda's saber is a good middle ground, and does well to imply that we've seen the extent to which Yoda is able to perform physical feats.