[Closed] Amsterdam to Copenhagen - where to visit in between?

So in true clueless fashion I seem to have been nominated holiday rep for the family trip to Copenhagen in the summer. Getting the ferry from Newcastle to Amsterdam and driving from there. I thought I might tap the STW hive mind and ask for any suggestions of places to visit in between the two? Four of us, but probably places of interest to a 2 1/2 year old who loves cars, bikes, trains, boats etc...?

I remember seeing bits on Coast about the North Sea coast of Holland that looked nice but no real idea where they were. Don't really want to hop on the motorway system and zoom through so if anyone knows anywhere roughly between the two places we can stop off to break up the journey, it'd be much appreciated!