Don't sweat the potty training. If it happens before, great. If not, no biggie. And I totally agree with early poster on just going with naps in the stroller whenever and wherever they happen. In the 10 trips I've been on with at least one child under the age of 3, not once has my under 3 year old child napped in the room in the afternoon.
I've taken both of my boys to WDW just before they turned 2 (hey, free flight!). The first came back a different child. The characters weren't just pictures in a story book or from a cartoon anymore, they were each "my fiend" ____ (he couldn't say the "r" in friend yet). He was convinced that when Mickey, Minnie, etc. waved at the crowd they were waving at HIM. It helped that we went to a few character meals (BIG hit with mine, but some kids are scared -- make sure you buy the Sing Along Songs DVDs with the "real" characters and show them before you go) where he got personal attention from the characters, but even the ones we saw from afar were "my fiends". To this day he loves parades and live performances. Younger brother started going as an infant and heard big bro calling them all "friends", so they're his friends, too!
So a couple of days (or partial days that = a couple of days) in the Magic Kingdom is a must do. Lots of characters, parades, the castle stage show, etc., plus traditional rides like IaSW. And mix it up - two rides, play time in the New Fantasyland area with the misters/fountains, a ride, snack time, a ride, the castle stage show, etc. Don't try to do back to back rides, rides, rides, rides all day. And note that you might want to NOT do Fastpass+ at Dumbo and Pooh --- as the waiting areas have fun things to do that might be even bigger hits than the rides themselves. And learn where all the little kid playground-type areas are in every park. Some, like the spot in MK's Frontierland between Splash and Thunder Mountains by the train station, are pretty tucked away.
Don't skip the small stuff -- like those street performances in Animal Kingdom (and by the way AK was a huge hit with both boys on those early trips -- the Boneyard playground and the train ride out to the petting zoo area -- don't miss those!). I can't prove that those drummers in the Harambi/Africa area are the reason my oldest (now 8) loves playing percussion instruments and is in his school's performance troupe now, but I'm sure that smile he had on his face when he saw them for the first time was something I'll never forget. The same for watching the Nemo and Festival of the Lion King shows. AMAZING performances. And don't forget the animal trails and the safari ride! Spend at least one full day (or parts of two days if you park hop - which I suggest) in Animal Kingdom!
With a little one I'd suggest a half day or parts of two days in Hollywood Studios. The Disney Jr. live show (think big puppets) is fun. And be there at rope drop if you want to do Toy Story Mania. If you stay on property (I suggest Art of Animation - not on the monorail line but the themed areas, especially the Nemo pool and splash area, are the BEST for little kids) then you can do EMH evenings, where every time I've been to HS they had a character dance party in that same Disney Jr. spot. I literally had to drag my then 1.5 yo youngest out of that place at like 11 pm because he was so tired he couldn't see straight, but he just wanted to keep dancing with "Jakey" (of the Neverland Pirates fame). And the Hollywood and Vine character breakfast or lunch has Disney Jr. characters (they change periodically).
Epcot has a few things that are really fun for toddlers. The Seas has the Nemo ride plus the amazing aquarium and Turtle Talk with Crush. The Land has the Seeds boat ride and the best food court food for kids anywhere in WDW. Mexico has a fun boat ride (a lot like IaSW - so go inside and look for it!). Mission Space has a tucked away INDOOR playground-type area called Space Base (enter through the gift shop and turn right). And there are fun shows/performances in several of the countries, plus Norway has the character meal with 3 or more princesses! So it is worth spending some time there, especially if mom and dad want to check out the food (and beverage!) options in the various countries.
I suggest park hopper passes with the morning in Hollywood Studios, take the boat ride (a GREAT place for a stroller nap) to Epcot for the afternoon and stay through dinner, then take the monorail to MK for evening parade/fireworks on the 1st park day. Next, take a day off from the parks and do character breakfast (say Poly's Ohana), play at the hotel pool and explore AofA and PopCentury hotel grounds, then early to bed. Next day do AK in morning through afternoon, then Epcot in the evening for dinner and Illuminations. Consider another no park pool and/or character breakfast or lunch day next or just pick a park for a short time (say MK to see daytime parades/shows or Epcot to focus on the princess character meal). Third full park day do MK from rope drop until early dinner, then take boat over to Ft. Wilderness and do Chip and Dale's campfire/sing-along and roast marshmallows. Just don't try to do parks, parks, parks, with rides, rides, rides every day. Mix it ALL up!