Since you are going in April I and have only one day, go to DL and skip CA. CA is under construction and while a lot of the park remains open, the pathways are obstructed and it will take you longer to get around. You don't want to waste that much time.
While some say you should take in the stuff you want to do first, I suggest you plan a sweep through the park to eliminate backtracking. You can easily waste scads of time running from one place to the next, even though everything in DL is much closer together than at WDW. I usually recommend starting with Fantasyland because those ride queues get long really fast, but DH at 12 may prefer rides like Space Mountain and Star Tours even more.
So, with that, consider starting to the right and grap a fastpass to Star Tours and then head over to Space Mountain and hop aboard. Then go over to Autopia. Unless he is really into Nemo, skip that one. If he is into Nemo, skip Autopia and ride Nemo. If you've got to do both, plan to do Autopia later in the day as an "if you have time" ride. You should be able to hit up Star Tours by now and then do Buzz.
From there, head across the plaza to Adventurland and pick up a fastpass to Indy, then do the Jungle Cruise and Pirates and maybe BTMRR. Then hit up Indy. Next, get a fastpass to Splash then do Haunted Mansion and maybe take a trip over to the island, but only if he really wants to. That place is fun, but it takes a lot of time. Then do Splash.
From there, take the train from NOS to ToonTown station. Head over Roger Rabbit and Gadgets Go Coaster and explore a little. If he really wants to ... stand in line for Mickey or Minnie, but with only one day, I'd say ... skip it. Those lines are pretty long for a picture. Then head out to Small World and then over to Fantasyland.
That will take you on a big swing around the park and get in the "majors".
If you want to fit in the parade, Fantasmic and fireworks or if he is into the Mark Twain or Columbia, then you'll have to look into where those fit on that "swing" and decide if you have time. One day isn't a lot but if you plan to go for the entire time, you can really get a lot done.
My point about the above isn't to give you a complete guide, but a guideline or suggestion about how to minimize the time you spend criss-crossing the park. You really do lose a lot of time when you do that. Bring snacks in a backpack to eat on the go and plan one sit-down meal for early afternoon (2-4). You will miss the lunch and dinner crowds that way.
Keep an eye on your watch as you move through the park. You will go quickly if you get there early and will slow down as the morning wears on. If you stay through to close, you'll likely pick up a few additional rides near the end of your day with short lines.
The early bird gets the worm. Pace yourself and you can make it from open to close. Go hard and you'll burn out.
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