About the surprise part - does she LIKE surprises or hate them? I agree, if you let her know too much in advance, it might feel like pressure. But just be careful she's not one of those people who like advance notice about everything and don't like sudden changes in plans - if so, then give her some kind of warning, like "keep Saturday night free, okay?".
Also - I read somewhere that when dating, shared activities that involve adrenaline rushes (rollercoaster, scary movie, etc.) help make someone fall in love with you. Got anything like that available? Then dinner and EARLY to bed - don't get there at 11:00 pm and expect her to be raring to go
