Additional Nunchucks arent really necessary since most 4P games dont require them(i.e Wii Tennis) Probably recommend getting one more numchuck for the second Wii Remote you have
The charge station I got is the Wii Dual Charge Station and it works great. Definate pickup imo.
Some games that are a must have would be.. Zelda: Twilight Princess, Medal of Honor 2: Heroes, Super Mario Galaxy(Great Game) and Mario Strikers Charged(This one is online)
I dont know about Harry Potter but Pokemon Revolution was pretty much a waste of 50 bucks for me -_- Not much to do in the game unless you have the DS Pokemon games