Maarten's place is really a nice place with kids (ours are 7 and 10), you are close from the center but meanwhile away from the crowd and the tourist flow. There is a small playground area just in front of the houseboat so kids can easily go and play by themselves and you can keep an eye on them. There are very nice places to have breakfast or beer in the evening just next to the houseboat, you can walk along the Prinsengracht canal and find nice little streets on each side where there are small shops and cafés.
The houseboat has a large and cosy living room to spend time in late in the day with kids and bedrooms are nice too. We really loved the furniture too.
I really recommend this place, we had a really great time!