When we honeymooned @ WDW 10 years ago, they had horse drawn carriage rides available at Ft. Wilderness (I assume the still do). We had a bottle of champagne & timed it so that we could see the fireworks @ MK through the trees. Very nice!
For our 9th anniversary we had dinner w/Chip, Dale, Mickey & Minnie @ the Garden Grill. Low key, but the characters made a big fuss over us & that was fun!
This year on our 10th anniversary we had dinner @ Teppanyaki (sp?) to celebrate and had a cake. I picked up a cake topper and they decorated the cake w/sprinkles & then added our topper. We ordered the cake through the restaurant,and it was enough for all 8 people at the table -- so we were able to celebrate w/everyone there that night.
Other random thoughts...
--Chocolates from the confectioners on Main Street @ MK or Downtown Disney. The strawberries dipped in white chocolate are tooooo delicious!
--Cirque du Solei tix & a nice dinner @ Downtown Disney
-- Dinner @ Cinderella's castle & arrange to have a tierra/glass slipper delivered to the table for her. (A friend of mine did this for her Mom & she said there wasn't a dry eye at the table!)
It really depends on your wife, what she likes and her preferences. (As you can tell...my preferences run towards food!)