We've always stayed on site, so for a detailed itinerary, I can't really give you one. When we feel the family has had enough, we head back to the resort for a break then head out again in the evening.
When my son was 2 the craziest things excited him. He loved running over the bridge from the Crystal Palace to Adventure Land - over and over and over again. He loved all the fountains and especially the puddles. My point here is we were so upset that anything entertained him. Here we're in WDW so excited for him and he wanted to play with the simplist things. So just expect that.
My son at 2 year old was somewhat fearless the only thing that startled him was the 3D rides. Too loud. He loved the Tiki Birds (which I found scary at times), he loved the pirates, and all the other rides in MK. The only one we still haven't done with him is Mickey's Philharmonic because now I have a 9month old that I thought would get scared. One word of caution, watch out on Peter Pan, since your elevated, if your not holding on to him tight he can slip out from under the protective bar. We rode that once and never again until my youngest is older.
At this age, I would make sure to plan character meals. They get to spend so much more time with the characters. Crystal Palace and Chef Mickey's are two of our favorites.
AK make sure to get a fastpass ASAP for the safari. He'll enjoy it. My kids also loved seeing the animals on the walking trails. They also LOVE the Pocohantas show, for our family it's a must see several times.
EPCOT my son loves the interactive kids computers in Innovations. I on the other hand get bored in there, but he and DH love it. Nemo is also a huge hit for the little ones. Oh and the boat ride at The Land.
MGM is not a favorite of ours with little kids, not really a lot to do. Play and Dine with the Little Einsteins at Hollywood and Vine was the highlight of my son's vacation. He has a crush on June and I told her and it was just so cute. She made such a fuss over him and we got really cute pictures. JoJo was amazing with the baby. She picked him up and played with him for 15 mins. Playhouse Disney is a must, although it's not current (they're updating it in Jan). We did the backstage tour and no one was scared, they enjoyed the tram ride. Other than that, we lasted about 3 hours at MGM. Go there at night and see the Spectacle of Lights - that was amazing!
DownTown Disney (DTD) is alot of fun for the little ones. My kids love the fountains, the
lego store and of course the Once Upon a Toy Store. Rain Forest Cafe (RFC) is also a great place to dine with little ones.
Overall, once we had kids, the itinerary went out the window. Everything is about them. Where they want to dine, go, etc... I make reservations and half the time our plans change. My son loves eating hot dogs at Casey's and Pizza at Pizza Planet. DH truly misses the days of dining at the Brown Derby. Secretly, we dream of the days when the boys are in college and we can take trips to WDW without them!
In your case, I would just plan to spend a day at MK, AK and split your last day between a morning at MGM and afternoon at EPCOT. Go to DTD in the evenings.
Should you plan any fireworks, MK is nice for the kids. EPCOT is way too loud and will really scare him. The parades are beautiful everywhere but you might be worn out by parade time (we usually are).
Edited to add: Before my son's first trip to WDW, I bought him all the Disney Sing Along DVDs. Especially the "
Disneyland Fun" one. It's a day in MK (CA, but he doesn't know) with the characters going on rides with kids. He loves it and watches it still after 4 years! It got him really comfortable with the characters. I think that's a bigger issue than the rides. Some kids freak when they see a 6 Foot tall mouse, my son ran to him and hugged his legs!
Hope that helps somewhat. Have fun!
Mare