The right movement is the one that feels good, gives you the desired result and doesn't lead to injury. You should experiment with the different possibilities until you find the proper way.
This situation comes up all the time, not just with Beethoven. Sometimes, the first note is held while the others come in, somtimes it is not. If it is held, the easiest would probably be to drop the hand onto the other notes by rotating the forearm. If the notes are legato or detached, you have a myriad of possibilities. Forearm rotation is one of them. Another one is to play the first note, then raise the wrist and let the hand drop onto the other notes by lowering the wrist. The whole thing is akin to bouncing. Another way is to play the first note, then lower the wrist and strike the other two notes by moving the arm in while raising the wrist, i.e. in a forward scooping motion. This works well when the first note is accented and the following ones are not (e.g. at the end of a phrase). Then, of course, you could combine all those motions in various ways. If the notes are detached, you can lift the entire hand and move it over. Etc.
That's just the tip of the iceberg(TM)
Topic: Wrist Rotation Q