Best Places to ride bike with kids

Every part of the country has its charms and offers excellent, safe bicycle routes (see: http://en.routeplanner.fietsersbond.nl/#?utm_source=Google&utm_medium=CPC&utm_term=Fietsrouteplanner&utm_campaign=Grants&gclid=CN_o4ajNxsgCFaIIwwodzGkFdQ), and there dozens of railway stations where you can rent a bike for a daytrip (for an overview: http://www.nederlandfietsland.nl/alles-over-fietsen/fietsvervoer-en-verhuur/fietsverhuur-ns-stations#).
So it mostly depends on what you - and the family - are interested in. You can take the train to Purmerend and have trip around and through one of the most famous 17th century land reclamations, through De Rijp to Schermerhorn, and then slowly back to Purmerend. Or go to Gouda for a older landscape, and have a relaxed ride along the small river Vlist to historical Schoonhoven, and maybe take the river ferry to explore the other side.

The Waterland area just across the river from Amsterdam is a good bet. Perfectly flat, very scenic, and goes for miles up to the villages of Volendam and Marken. There's a little free ferry departing from just behind the Central Train Station that takes pedestrians and cyclists on a 60 second crossing, then it's all dedicated bike paths (ie no vehicle traffic) for very pleasant rides thru the scenic Poulder countryside. Can easily spend a day (or 3 as we did) just meandering, stopping for lunch, taking photos, etc.
There's a rental bike shop right behind the train station, and they sell a quite detailed cycling map there for a couple of Euros.

If you are in decent shape I like riding beyond Haarlem into the dunes towards Zandvoort. There are some really nice houses out that way. A lot of it is national park (Nationaal Park -Zuid Kennemerland)

Also, I like being south of Haarlem into the area around Heemstede and towards Lisse where Keukenhof (closed when you are there) where you can ride into woods and have a pancake.

Or a nice short ride northeast of Haarlem towards and around Spaarndam where "the boy put his finger in the dam".

And here a funny one on the other side of being a bicycle country: https://www.youtube.com/watch?v=-yTFiP_co0U

Thank you for all your suggestions.

We rode in the Vondelpark (more crowded) and in the Westerpark, more low key.

We also took the Waterland bus up to Edam and rode from there to Volendam and Monnickendam and back to Edam. That was a lot of riding but very open lanes and easy!

Kim