To avoid having two cars at the hotel, order a car to pick him up from the house. (A Towne Car won't cost much at all--maybe $50-75--especially just to pick him up at the house and drop him off at the hotel.) Lay out his clothes and pack a bag for him. You take everything with you besides whatever you want him to wear to meet you. Don't leave him responsible for bringing anything but himself. (Make lists, so you don't forget anything, like his underwear or razor. Tel him to shave before he leaves for work, so you can take the razor with you, but don't tell him that you want to take the razor with you! Just tell him that you want him to shave first and the reason is a surprise. He'll wonder, but he won't know until he gets home tha tyou've got something up your sleeve.) Go ahead of time to decorate the hotel room with candles and flowers. If you buy a candle or two at Bath and Body Works, you can get some sample scents to take with you. (Sensual Amber is very sexy.) You can also get a wallflower for the bathroom, so you don't have to go in there to blow it out before you go to sleep. Anyway, they're good about giving samples. Get some flowers--whatever you like, doesn't have to be roses--and sprinkle the petals outside the door. (Don't sprinkle them in the room, because they'll start to stink before the staff comes to vacuum.) Speak with the hotel staff (probably Housekeeping) about leaving the petals in the corridor until a certain time. Otherwise, they'll vacuum them up. Set flowers up in the room. You don't need to go out and get vases; just lay them across the vanity and the dresser, etc.
Don't leave him too many notes at home because he'll take too long to get to you. In fact, don't even talk to him after he gets home, and don't tell him that you're sending a car. Leave him in the dark, so you can maintain control. (That might make it more sexy for him, that you're taking charge--don't know your dynamic.) Have the car there by a certain time. Tip the driver and the doorman and maybe the concierge to give notes to your husband. Have one in the car when he gets in. Ask the driver to speak with the doorman, to alert him to your husband's arrival. That way, the doorman can greet him by name and maybe hand him a note or direct him to the concierge who will hand him a note. Each note will be sealed in an envelope--and maybe with a kiss--for discretion. Make the restaurant staff aware of the occasion, so they can seat you at an appropriate table, after he meets you at the bar (?). Maybe someone can suggest dancing within a mile. If so, see if there's a hotel shuttle that can transport you to and from--usually complimentary. If not, a cab should not cost too much for up to one mile. (If the weather and your shoes permit, you can walk if it's just a couple of blocks.)
I don't know how long you plan to stay--just the night or the entire weekend. Maybe you can invite some friends to join you for brunch on Saturday, and make a big deal of his birthday then.
PM me to work on those secret notes. (Can you tell that I am having way too much fun with this one? I love doing this kind of stuff with my husband...turning something ordinary into something special just by tweaking it a bit.)