My husband and I took a trip this fall, and I felt it was one of the most laid back trips we have done so far. We were forced to slow down as we now have a one and a half year old, and so we couldn't tour with the same intensity as before.
Based on our experiences, my tips would be
1) Use Fastpass Plus! One of the reasons we ran around a lot on previous trips was to get fastpasses for one ride, then go somewhere else until it was time to redeem it, and then have to go back over. But now with Fastpass Plus, we had all of the fastpasses taken care of ahead of time, and if it was time for a fastpass and we were all the way across the park, we could just go into
MDE and change it to something else.
2) If you aren't adverse to getting up early, go for rope drop. You can get so much done by noon, and then grab some lunch and leave. If you really want to relax, I would say to just spend the rest of the day enjoying your resort. (We always went back to the parks in the evening.)
3) Visit locations where you will spend a good chunk of time: You can easily spend an hour at The Seas, a few hours wandering the World Showcase, up to an hour seeing shows (the two at Animal Kingdom are very good, especially Festival of the Lion King.)
4) Most importantly--don't stress out if you miss stuff. We never got to ride anything in Tomorrowland our last trip. It just didn't work out that way. Sure, I was slightly bummed we missed TTA and Carousel of Progress, but we will get them next time--no sweat!