Thanks jeanm, MarkK, and Kenko for your replies!
We'll be staying one night at the Grande Fjord Hotel in Geiranger rather than going back the same day, just to increase the chances that there is one sunny day to enjoy the views.
It seems like best views of Geirangerfjord are from an elevation rather than from water level, which means that we would want to visit either Ljøen, Flydalsjuvet, and Ørnesvingen. If we take Hurtigruten to Geiranger, we won't be able to visit Ljøen (since it is near Hellesylt and we plan to return via Eidsdal). To visit Flydalsjuvet, we will need to find transportation from the Grande Fjord Hotel. On the way back to Alesund, I'm investigating whether we can hire a taxi to drive us to Eidsdal, and then take the ferry to Linge, so we can catch the 10:53 am bus from Linge to Alesund, via connection at Sjøholt (4 minute wait). That would bring us to Alesund around 12:45 pm, which would be perfect. The only concern I have is that if the 10:53 bus gets canceled from Linge, taking the next bus @ 2:53 pm could ruin our plans.
We will ask the taxi driver to stop at Ørnesvingen for a few minutes on our way to Eidsdal.
Am I missing anything in this plan? We won't have the convenience of a car in Geiranger to drive to/from the Grande Fjord Hotel to Flydalsjuvet. This would be an alternative to renting a car, driving from Alesund to Hellesylt, taking the Hellesylt to Geiranger ferry, and driving the next day back to Alesund via Eidsdal.