Your birthday is a pretty big deal on Facebook. If you use it a lot (or a little), you get to hear from dozens or hundreds of friends and family. Even if you know that all they did was click a link or take 30 seconds to jot a note, it still makes you feel special.
Kids love getting mail, especially on their birthday. Many children's ministries I know do a great job of making kids feel special by sending them a simple card on their day.