I am one of the last Brusselairs, ask my anything.
There are some interesting museums in Brussels, my favorite is the middle age section of the Art & History museum in Cinquentenaire, they recreated a cloister to put the artworks in.
The Old Master section in the Royal Museum of Fine Arts is also really worth it, maybe do the Magritte one too. The Museum of Musical Instruments was my favorite as a child.
The Grand Place is must do, I guess. The Cathedral is really pretty, Notre Dame du Sablon as well.
Stay in the center, don't try to go to the Atomium or Mini-Europe, it's too far and it's shit.
Nobody will stop you from drinking beer, maybe try place du Luxembourg, place des Anglais, Saint Boniface or Flagey in the evening.
There are no good ways to go from Charleroi to Brussels.
Be really careful around the South station, otherwise the touristic parts are not too bad.
And I agree with the post above that Ghent and Bruges are better for tourists than Brussels (I never understood how there are so many tourists in Brussels).