R2 and C-3PO are right outside the door when Bail, Yoda and Obi-Wan decide the fate of the twins. Bail gets up, goes into the hall, and gives the droids to Captain Antilles. It's all part of the same scene. They don't exist in the same room, but its suddenly a major stretch. Not to mention, it's pretty unlikely that R2 wouldn't know Yoda who Yoda is or what he looks like, given that he was (miraculously) in the service of Anakin and the Jedi in Episode III (as opposed to being in the service of Amidala and the Naboo, where he was in Ep I and II, and even The Clone Wars).

Now that I think even more about it, given that Anakin hadn't seen Padme for about 9 months leading up to the movie, how'd he pick up R2 in the first place?

I gotta file this stuff at IMDB.

EDIT:
They DO share screen time ... at the birth of the twins. Yoda, Obi-Wan, Bail, R2 and C-3PO are ALL in that corridor when the twins are born. I rest my case.