Itinerary looks good to me!
Muiderslot is worth visiting (if you enjoy biking this might be a fun place to visit by bike) and if you enjoy castles and historic houses there are a number of other places to visit in and around Amsterdam. I can heartily recommend the Museum van Loon, a seventeenth-century canal house that is owned by one of the descendants of the original signatories of the charter of the VOC, the most successful European East India Company and the first MNC with shares in the world. It gives a wonderful glimpse into the life of the Dutch merchant elite and how they lived in the 18th/19th centuries. The Portuguese Synagogue and Jewish Historical Museum are also worth your time. Don't forget to visit the Rijksmuseum, Stedelijk and Van Gogh, although there are many other museums also worth visiting.
I concur that Weesp is definitely worth visiting as are Enkhuizen and Hoorn (also important VOC towns back in the day). If the weather is good you should also try to get out on a boat on the canals. Those Dam Boat Guys get good reviews although I cannot vouch for them personally.
What are you hoping to see while you are here and what are your interests?