Hi Annette,
How exciting to be planning your child's first Disney World trip! I love that you are starting early, my boys have been going since they were four months old. There are numerous attractions and of course shows that you and your child will be able to enjoy together even though he is only six months old. Given the age, some of the "special treats" like firework cruises, tea parties and family tours, will not be as much fun for your child at this time.
My biggest suggestion is to capture everything! Be sure to take lots of pictures and video of the trip and his reaction to everything. Spend time, interacting with the characters and letting your child enjoy the sight and touch of Disney. Splash in the water, visit Mickey and Minnie's house in Toontown, dine with Donald, ride It's a Small World ten times, but whatever you decide to do, do it at your child's level. Slow down and let him take in the feel of Mickey's hand, the sound of the music, the sight of the parade floats and be sure to keep clicking and recording every minute of it. You may want to consider pre-ordering a PhotoPass CD, this way the PhotoPass photographers can capture pictures of your entire family on this memorable trip. You can find information
here.
I can tell you from experience, that my three boys don't "remember" their first Disney trips, but they still LOVE to take down the photo boxes, scrapbooks and videos and look at them again and again. They love to watch how they reacted when they were little. The experience of your child's first Disney trip at six months is something for you to treasure now-with pictures and video, it is something your child will treasure in the years to come.