Everybody is giving you great advice. You really do need to have park hopper tickets. And if your son is age 3 on the 1st day of the trip, then he needs a ticket, too.
Since you like taking it slow and not rushed, go for 5 days. We did that last summer and it was wonderful. And you know what? We still didn't do everything.
Since you're staying at the PPH, you'll get early entry (EMH) every day. At DL/DCA, it pays off to use EMH. It really does. It's GREAT! It pays off at DL to be there for rope drop because the first 3 hours that the park is open is the least busiest time of day. A lot of DL visitors live in So Cal and drive to get there, which means a lot of them don't show up until noon.
I disagree with the advice to wait on Toon Town until the evening. After a long day in the parks, by the evening your average 3 yr old will be really worn out. Here's what we've done before at DL. I recommend considering an itinerary something like this if you want to maximize your time in the mornings. I've done this myself a few times now and this really is do-able even with kids in strollers and time for bathroom breaks.
- Let's say reg. park opening is 9am. That means that DL EMH is 8-9 am. Be in line with park tickets in hand at 7:30 am. EMH at DL is on Tues, Thurs, or Sat.
- At around 7:40-7:45 am, they'll start letting people in. Go walk down Main Street for the rope drop.
- Walk with purpose to Fantasyland.
- If there's already a line at Peter Pan, skip it. Otherwise, go on...
- Peter Pan
- Dumbo
- Alice
- Mad Tea Party
- the carousel
- Snow White
- At about this point, it will be regular park opening time.
- Pinocchio
- I'm leaving out Matterhorn since your kids will likely not be able to ride it, but if you adults want to try it, ask a CM for a child swap pass.
- Storybook Land Canal Boats
- Casey Jr Circus Train
- bathroom break. There's 1 kind of between It's a small world, the entrance to Toon Town, and the Mickey & the Magical Map theater.
- Autopia
- then be at the entrance to Toon Town 5 min before it opens. It will open 1 hour after regular park opening.
- Walk then straight to Mickey's house to meet him with almost 0 wait time.
- The other main characters will be out on the "street" in Toon Town for meet & greets.
- Let your child explore all the fun stuff in Toon Town.
- Next head to your late character breakfast reservation at the Plaza Inn. Do something like a 10:30 am reservation. Sit and eat MIckey waffles and bacon for an hour while up to 7 characters come over to you. They're really great with little kids.
- Make sure at regular park opening time, that you get a FP for a FP ride.
- After the Plaza Inn, go on HM or Pirates.
- Then go on HM or Pirates (whichever one you didn't go on just before).
Winnie the Pooh always has a short line.
When the parks get busy, head to Tom Sawyer's Island and let your kids run around.