We had a short break in Bruges last year with my wife and 2 children (under 10), and stayed at the 'The Montanus Hotel', which is very near the market place and belfry. We decided to walk from the train station which only took around 10 minutes, (and helped to burn off some excess energy). We had a junior suite, which was really really spacious, and we had an additional 2 beds for the kids, but I am sure they must provide cots for younger kids. There was also a small garden. Q pricey but you don't get the option of a lobster breakfast in many of the hotels we have stayed in!