Please find a very nice summary of events in the region here: Steinhude
If you want to rent a bicycle while you are in Steinhude you can visit “Fahrradverleih und Minigolfanlage Steinhuder Meer“. Show your “participant card” and you will get a bike for 6 € a day (kids bike 3 € a day). Or play Minigolf for 2 €.
There will also be a discount in the tower at Wilhelmstein. You will get the best view across the lake from here.