My suggestion would be to research the bike rental shops in the vicinity of Centraal Station. They're all highly rated, have good quality bikes to rent, and have the advantage of being only a short pedal down to a cute little bicycle/pedestrian ferry that crosses the river. After you debark from the ferry you'll be in the very pleasant poulder countryside with nothing but easy cycling ahead of you. As was mentioned, it's about as flat as flat gets and so is no great challenge if you're reasonably fit. Still, I would think an ebike would be a good choice if you're not already avid cyclists and would just like a break from pedaling for a while. It would also extend your range if you want to explore a bit further afield. The ride up to the fishing village of Marken was a particular favorite of ours - it runs along the top of the dike next to the Ijmeer and is a very pretty way to go.
The bike shops all sell an excellent map of the dedicated bike trails in and around the city which is worth picking up. They also provide excellent advice for a day's ride geared to your particular interest. Point being that you may not need to book a tour - with the map and a pair of padded cycling shorts (you'll thank me later) you'll be good to go.
FWIW, might add that my wife really enjoyed our cycling trips out into the countryside but didn't particularly enjoy riding in the city - just too congested for her comfort level - hence the suggestion to start your ride at the bike ferry in order to get out of the city as quickly as possible.