I think that Doc should play House much more than in the previous games. Two reasons : Eddie is shooting something like 90% from anywhere on the floor in this series and the Magic struggled to contain him in the last game, so maybe they won't be able to prevent him from catching the ball... and if that happens, Eddie will make them pay and have a big game like in game 2.
So, a small lineup with Rondo/House/Ray/BBD or Scalabrine/Perkins could be very effective, but if Ray continues to struggle badly (by that I mean, not only missing his shots but making poor decisions/passes) put a lineup of Rondo/House/Pierce/BBD or Scal/Perkins.
The idea is to space the floor so that Orlando must stay on each shooter, allowing the Celtics to go in the paint or make good passes.
Other than that, good defense for 48 minutes, good rebounding and Ubuntu are the priority for Boston. Let Howard play one on one against Perkins, and stay close to the shooters, and everything will be OK. Dwight scores only on alley-oops, offensive rebounds or pick & rolls.