Fantastic, you've got tons of time.
Flowers - Unless you have specific information knowing that your wife hates flowers, it's a good idea to order some. Arrange for them to be delivered as early in the morning to her work as possible. It will set the tone for the day and let her know that you've thought ahead. Roses are good if you're going for the straight romance route. If she's more into nature then a variety of flowers would be good. Remember, the more people that see them at her work the more points you get.
Notes - Women love little notes. If you can't think of what to write yourself (I can't), there are packages of sticky notes with little drawings and feel good sayings on them. You still get credit for saying them to her, but you didn't have to come up with it on your own.
Babysitter - Sounds like you've got this taken care of. Luckily your wife's birthday is XXXXX a Friday this year. Is an overnight date an option?
The Date - Is there a spot where you and your wife used to go when you first started dating? Recreating an important date that the two of you had would go over well. Something that jogs her memory about how much you wanted to impress her, etc.
How about the spa? This last year I sent my wife to a spa and while she was there about 25 people came over for a surprise party. If you shop wisely at Costco, you could supply quite a lot of food for $300. Maybe have everyone bring over a bottle of wine or their favorite drink?
CitySearch.com - A great resource to find out what's great for dates. Users write reviews of restaurants/bars/hotels etc. They even have a "Romance" category. That's a great way to find out what is good in your area, especially if you want to go out somewhere new.
Romance packages - Most nice hotels have packages you can order ahead of time. They could include credits for romantic dinner, room service breakfast, champagne, roses, bubble bath and so one.
Without knowing more about your wife this is about all I can think of for recommendations..... If it's obvious that you've put in a lot of time and thought for her I'm sure she will love it.
I hope this was of some help to you. If so, please don't forget to "Accept"