I purchased both the Unofficial Guide and Birnbaum's when I was planning our 2003 trip, mainly because my friend (lives in another state) doesn't use a computer and I wanted her to participate!
Quite honestly, I found this and several other unofficial sites, as well as the Disney official site, much more useful.
While you want to plan, don't overplan, particularly with a toddler. You'll end up zagging when you planned to zig, which can be frustrating!
Depending on the length of you visit, plan one or two character meals if your little one likes that sort of thing. Plan attractions/rides that really interest the adults in your party and things you think your little one will enjoy. Use the baby swap with other adults in your party for adult rides. Be prepared to exit an attraction or hold and comfort your little one if reality doesn't quite match anticipation on a ride that you can't exit until the end.
Plan breaks. Inside the parks, find a place where your toddler can, well--toddle! I really feel sorry for all of the little ones who are whisked from place to place in a stroller all day for the convenience of the adults! If you're staying on site, take a nap break in your room. The adults may be ready for it, too!
Otherwise, find a quiet nook and settle in for an hour or so.
Use common sense, pay attention to the needs of your little one, and you'll all have a magical visit!
Kapp 
