I take DD to Amsterdam almost every year. I love it, it is a wonderful destination for families who are content to poke around and let a lovely city reveal itself. Very low key, always delightful.
My favourite places-
Kinderkookcafe
This is a cafe/play centre on the edge of vondel park. Children ages 3 - 10 pay a very small fee, and they are given all the ingrediants they need to make their own lunch. Then, in an impecably appointed kitchen, they prepare and cook their own lunch, and yours if you want. You- sit in the garden with a cold drink and a good book, kids- in the little kitchen slaving over a hot stove deliriously happy.
There is usually no need to make an appointment, there are no set class times, just turn up and pay 3 - 6 euros per kid, depending on the recipe they end up using.
www.kinderkookkafe.nl/
Cafe Restaurant Amsterdam
Probably my favourite restaurant on the planet. It is slightly out of the city centre, so tourists rarely make it out. It is however, about 2 min walk from where the number 10 tram terminates, so very easy to get to. It is an old massive turbin hall, (think tate modern) so an epic size. Lovely service, perfect simple food, reasonably priced, incredible atmosphere, pure amsterdam- a combination of modern, historical, edgy, traditional.You could turn up order a coffee and a piece of toast, or champagne and oysters for the whole table and you will be treated the same- relaxed, casual efficient. Not many places offer £200 bottles of wine and kids colouring sets at the same table. Sophisticated, glamorous, urban family dining at its absolute best. Yes I am gushing, but everyone we have ever taken here has left dropped-jawed.
www.cradam.nl/
St Nicholas Boat Club
This is a small group of bonkers expats who run boat trips around the canals in tiny little run around open top old fashioned wooden boats. Like the best of Amsterdam it is slightly anarchic in a "go round the back knock 3 times and ask for frank" sort of way. Much nicer than the massive canal boat tours. Sitting slightly above water level, wind in your hair, not a kid in the city who wouldn't jump at the chance.
amsterdamboatclub.com/faq.html