Here's what I did for my wife's last bday,
Lined up a baby sitter for the night
Made hotel reservations (same place we got married 5 years at carriage house inn)
Made dinner reservations at one of her top 5 restaurants
When all is set, Sneak out of the house and Check into the hotel room early, plant rose petals all over the room/bed ( can buy bags of them at Safeway) champagne and chocolate covered strawberries displayed
Take her for dinner, enjoy a great meal and a few drinks hit up a comedy show then surprise her with the hotel atmosphere