Family accommodation for 4 in Amsterdam

Hi everyone, My family and I are stopping in Amsterdam for a couple of nights in late March 2010. We are two adults and two kids (aged 4 and 7) and haven't been to Amsterdam before. I am really struggling to find a hotel for us that isn't too expensive. Probably looking at USD100 a night (or thereabouts) and 3 stars plus. Or is unrealistic?

Also, no idea what location to stay. A friend of mine suggested "south" of Dam Square, as there was a tram that could take us into the main tourist areas. He wasn't much help to be honest!

Thanks everyone - any advice or suggestions are welcome, cheers