DL with a 4 year old and a 4 month old? Here is what I would do:
Eat in car on way to park
Take train to Fantasyland
Get in line for Dumbo, ride Dumbo
Get in line for Peter Pan, ride Peter Pan
Ride carousel (line moves pretty fast)
Ride Tea Cups but don't move wheel
Head to Adventureland and sit through Tiki Room and Jungle Cruise
Head to Frontierland and see Woody and maybe Jessie. Look at ground where they have hoofprints in the ground.
Go to Tomorrowland and ride Buzz Lightyear and MAYBE the Matterhorn-depends on your 4 yr. old. My DD3 loved it except for the Yeti...
If you do a character meal, the Princess meal in DCA is AMAZING!!! Guaranteed to see at least 4 Princesses and usually lots more! 3 times and we have seen Princess Minnie, Mulan, Snow White, Aurora, Cinderella, Ariel and Pocahontas.
Go to New Orleans Square and again, DEPENDING ON YOUR CHILD, ride PoTC and HM-4 month old can ride both but hold tight on PoTC. Take a cruise on the Mark Twain.
Evening-go to Fantasyland and ride IASWH where the lights will take your breath away and the carols will soothe your nerves. INCREDIBLY huge line here.
I love holidays at DL and this will be the first time in 4 years I haven't been there for them-how will they ever get along without me?! LOL Have a great time and just relax! Go with the flow!!