Day trips from Amsterdam

Sorry don't know Geithoorn. We took wonderful day trips to Kinderdijk with Rotterdam, Delft, Leiden, The Hague and Haarlem, excellent train service.

According to 9292.nl/en, it is just over 2 hours with a train change and a bus for the final leg. 24.47 EUR each way.

I wouldn't think almost five hours travelling to and from Giethoorn is worth the experience. Moreover, the Chinese having discovered it as the »ultimate Dutch village«, it might be uncomfortably crowded on a bad day.
But the east is a nice part of the country with a feel which is different from the west (the »Holland« part of the Netherlands). The IJssel river has a string of historical Hansa cities, all of them worth a visit. Kampen has the best river front, and Zutphen is possibly the best preserved. With an early start you can combine those two on a day trip. (Use the train planner of NS, the national railways, or the general public transportplanner 9292.nl.)