Our family of four is flying to Amsterdam Dec. 23 to visit our daughter. We also want to see Belgium, France (Paris) and maybe Germany. We are staying through Jan. 1. We're looking for suggestions on cities/sites to see, places to stay, etc. We plan on getting rail passes.
I count 8 or possibly 9 full days on the ground for sight-seeing, not counting the flying in and flying out days. And it appears you'll be spending part of that 8 days visiting your daughter. Depending on how much time you spend in Amsterdam visiting your daughter, your full days for sight-seeing outside of Amsterdam are fairly limited. You say "and maybe Germany." It may be that you'll enjoy your visit more if you leave Germany for your next trip and in the time you have enjoy the Netherlands, Belgium, and Paris. You didn't mention where you're flying out of, Paris or Amsterdam, if Amsterdam you'll have to allow time to travel back to Amsterdam.