Here's a thread with a trip report from last year where the poster tells about an anniversary trip.
http://www.disboards.com/showthread.php?t=3161590
I've also been to DLR several times solo after working a shift on business trips in Southern California. While I found it somewhat lonely, and definitely better to go with others, it's also great to be able to experience some things that you find a priority but young children might not. I would suggest really enjoying shows and some of the park atmosphere, like the themed performers that are often scheduled for places like Buena Vista Street and New Orleans Square. Young children may not have patience for some of those types of things.
Also, some things that might seem really costly to do with children, might not seem too unreasonable for just the price of two people. For example, the guided tours or some of the fancier or more expensive table service restaurants might be a special treat for an anniversary celebration. I find that as adults, we tend to appreciate those types of things more than a young child might. So the value of them is increased even more.
Also, don't forget to pick up anniversary celebration buttons. You can get them from City Hall in DL or Chamber of Commerce in DCA. Other shops, like World of Disney in Downtown Disney, often carry them as well. Performers and other cast members will notice them and go out of their way to really make your celebration special. You may even get some free desserts from table service restaurants!
Finally, I would suggest finding ways to capture memories of the special trip. Certainly photos are a great way to do that. You can almost always find someone willing to take your picture for you. PhotoPass+ may also be a great way to capture memories. If you are into character meet and greets, photos with just you and your spouse and a character can be such a great memento. But even more personal and special might be to do a couple silhouette at the Silhouette Studio on Main Street. They can put the silhouette of both of you into one frame.