I actually just got back from a short trip myself. I'm used to week-long vacations, so when I realized I had only two days to cram everything in (I was already in Orlando for a conference), I was scared I wouldn't enjoy myself at all. Luckily, I did.
My advice: sit down well in advance of your trip and decide what you really want to do. What's your favorite thing about the World? Restaurants? Shows? Rides? What would you absolutely not want to miss on your anniversary? Plan your trip around that.
For my trip, I was going with a first-timer and we wanted to maximize our time for rides and attractions, so we decided in advance to eat only counter service and not bother with table service meals. Since it's your anniversary, you might want to schedule a nice table-service meal in a romantic setting, but keep in mind that there's a trade-off involved. Table service takes a lot longer, and it requires you to stop what you're doing early to head towards the restaurant in time for your reservation, so it can take a lot out of your day. Decide whether you'd rather have the extra park time or the nice dinner. If you decide on dinner, get your reservation as soon as possible, since many restaurants book up quite early.
Then spend a little time deciding what you really want to do on this trip. Do you have a few favorite attractions that you really want to experience on your anniversary? Is there anything new or changed at the parks since your last trip that you'd love to try? Keep reminding yourselves that you won't be able to do everything you enjoy, so keep your "favorites" list to a minimum. If you have extra time, you can do more things, but it's best to get your top choices in first.
You've got two nights, so that means you could see two of the nighttime shows. Which are your favorites? Mine are Wishes and Fantasmic, but yours may be different. Plan your days so that you'll end up in those parks on your two evenings, if you want to see the shows.
If any of your "must see" attractions for this trip are super-popular (such as Soarin'), make a point of getting to these first to experience or FastPass them. But don't overplan your day, because that will just stress you out. If you know where you're going to start, you know where you're going to end, and you know some of the things you'd like to do, you should be able to play it by ear and enjoy yourselves while making the most of your trip.
Those are my suggestions, anyway, and they worked well for me on my recent (too short!) two-day trip to the World.
Have an awesome time!
-p.b.
