I would already consider a "sportscoat" to be rather casual. And regarding seats: I now depends a bit whether you guys are vertically or horizontally big. First row might give you more legroom, however seat width should be always the same.

Budapest has a nice muscial theatre where you can experience broadway blockbusters in Hungarian language. Quite interesting. Beside that: Tons of very good restaurants in the city and tons of other options depending on your preferences.