My little guys have been going since they were 3 months old. Duncan used to love the characters, this past trip he went into the terrified mode. However, when it came to rides, watching shows and interacting with CMs, he was in heaven.
Only you know your children the best. Ride descriptions are one thing, actually going on them is another. Duncan (who turned 3 in Feb 2009) ADORES the carousel, so we start there EVERY trip at his request. Then we move onto Small World, Peter Pan, Dumbo, etc. He turned into a big roller coaster junkie on our last trip, and refused to go on the "Baby Barnstormer", it's all about Big Thunder nowadays.
I used to think skipping EPCOT was wonderful - but Duncan and Pierce can't get enough of the Nemo ride. For some reason, they are also addicted to Figment (Journey Into Imagination). Not to mention Duncan has reached the point where doing the Kidcot activities and hands on demos now appeal to him. The CM's "around the world" were incredible with kids, from teaching him hello in their mother tongue to sharing the odd candy treat (a CM in Japan gave Duncan a couple different hard candies she loves, and he was was on cloud nine).
For us, we've reached the point skipping parks no longer happens. We go with the flow, since every day brings a new adventure. Let your kids test out the rides or activities at their own pace, and allow them to interact with the other children. You'll find little kids are the greatest motivator for each other, and once yours see the excitement, the bug will bite.