I'm from the Netherlands!!!!!!
Please feel free to pm or mail me it's no problem at all to help out a bit.
What are you interested in??
Because there is so much to see and do (you already figured that out).
In Amsterdam you have the city by itself but also the van Gogh Museum and the Rijksmuseum.
You can do a boattour around the city in the canals.
Ofcourse it's nice to do some shopping (very expensive for you guys) but even if you don't buy anything it's great to see the shops (it's no mall but just streets with shops).
Daytours:
In april you can visit the Keukenhof this is a place with lots and lots of flowers (tulips) and tourists love this place. -> this you can do by train to Leiden and then a bus (maybe a bus from Amsterdam also) and thru a organized tour.
You can take a tour (organized) to Volendam this is a fishermans city.
Delft the place where i live is beautiful (tourist say that) there is the possibility of doing a boattour thru the canals and climb the church 108 meters high and the second highest church in The Netherlands and all the royals are buried in this church.
Also Delft is the city of the Delft Blue Pottery. -> Just an easy train ride (45 min) from Amsterdam.
http://www.delft.nl/webEN/content.jsp?objectid=33500
http://www.delfttoerisme.nl/eng/index.shtml
http://www.royaldelft.com/nederlands.html
In Den Haag (the Hague) there is Madurodam, that is a miniature city with all the highlights of the Netherlands in it.
The queen lives in Den Haag and you can visit the palace gardens.
The Parliament is located in Den Haag (Binnenhof) and you can stroll around.
Also located in Den Haag is het vredespaleis (peace palace), there are some guided tours available. The gardens are beautiful to visit. -> a trainride away from Amsterdam (30 min).
http://www.vredespaleis.nl/showpage.asp?pag_id=429
http://www.madurodam.nl/templates/mad/global/index.php?lngid=5&sqlmode=1&fid=638
Also Rotterdam is a city you can visit.
There is the Euromast.
Rotterdam has the largest or second largest port/harbor of the world.
What i would recommend if you go to Rotterdam is see the Euromast and then make a boattour on the Pannenkoekenboot (link provided, only Dutch, btw there is also one in Amsterdam) this is typical Dutch food.
http://www.euromast.nl/english/index.html
http://www.pannenkoekenboot.nl/ (if you are interested i can translate for you).
If you plan to visit Delft, Rotterdam or Den Haag just give me a PM or mail maybe we can meet each other!!
That would really be nice, so don't hesitate to do so.
It's even possible for me to come to Amsterdam if you like (it's just a small ride anyway here in the Netherlands).
There is lots more to see and do, again please feel free to inquire some more information.
Just give me some things that you are interested in and maybe i come up with some other things.
Also please let me know what you already thought you wanted to see and do, maybe i have some interesting pointers for you.