And had a great time. Just take it easy. We did pretty much everything and he did well. We used baby swap for our "must do rides"--Test Track and Tower of Terror, but we took him on pretty much anything we could.
We loved walking around World Showcase and since you'll be staying at the Polynesian take advantage of the monorail. Choose to go to MK or Epcot in the evening so you can avoid the buses in the evening hours; it makes it easier that you can let the kids relax in their stroller and not have to take them out for the ride home. Bring pjs when out at night. Many nights we were able to get our little guy to sleep in the stroller and then watch Illuminations and walk around the World Showcase until we were one of the last visitors left (its one of our favorite things to do; it's such a peaceful and unique experience) and then walk back to our hotel (we were staying at the Dolphin). We felt like there is very little to do at the Studios for little ones- Playhouse Disney, Honey I Shrunk Kids playground, Little Mermaid (can be a little scary). We normally only do a half day there- we love 50s Prime Time and we do always have to do Tower of Terror but many of the shows and attractions are geared towards older kids. They do have lots of characters there that other parks don't have but a 20 mnth old may not be too interested in the characters.
We tried going back to the hotel for naps but he wasn't a good napper in strange places so most days he would nap in the stroller and we would try to time it with a long lunch and he would snooze in the stroller while we had a leisurely meal (a rareity). Most of the sit down restaurants allowed us to bring in stroller; if they didn't we just wouldn't eat there and try somewhere else or eat at a counter service. When we went again when he was 2 1/2 he napped like a champ and the three of us would go back to the hotel every afternoon and take 3 hour naps --it was the most relaxing vacation ever. My advice if your child will nap in the hotel room go back and relax or nap; we are headed down in a couple of weeks with our 4 1/2 year old and 1 1/2 year old. I know 1 1/2 year old will nap every day. DH and I are going to do rock paper scissor to see who gets to go back to hotel and nap with the little one every day.
All restaurants the kids are the norm not the exception so eat where you want to eat. Ride the rides you would normally ride and see the shows you would normally want to see (except watch out for the loud ones--mostly at Studios). Relax and have fun!!!!