There's plenty of museums in Amsterdam to go to (if you like that sort of thing) including doing the conga through Anne Frank's house, which was a close favourite behind the Heineken Museum.Like the afore mentioned if you are struggling,you can get trains to other cities which only take 45 mins tops.The best of these would be Alkmaar,Haarlem,Leiden,Utrecht,Den Haag and even Rotterdam.You also have the smaller towns like Delft,Gouda,Edam,Enkhuizen & Hoorn,which are all special in their own way.I suspect that this may be your 1st time over there,so I think there will be enough for you and the missus to keep you's occupied.
This website might help you out further as it has done with me over the years
http://www.inyourpocket.com/Netherlands/Amsterdam