^ Excellent suggestion. The best whipped cream ice cream for under a euro.
Check out Café Alto or Bourbon Street if you want to have a great night and like jazz/soul/blues/good music. They're just next to the Leidseplein. Close to the Leidseplein is also Everything On A Stick, a restaurant where...well, you get it.
And before you leave, for god's sake, go by La Perla. It's the best pizza place in Amsterdam. It's in the Jordaan (Tweede Tuindwarsstraat). It's amazing. And if you want to go for some nice Belgian or Dutch beer in a cosy environment, go see 'skek at the beginning of the Zeedijk (close to central station).