We always do relaxed trips. We don't even make fastpasses ahead of time since we never know what we're going to feel like doing that particular day or time. We do make same day fastpasses while we're there, but don't stress about anything. We've been on all the rides and attractions more times than I can even begin to count, so we just take things as the come.
Attractions that I really enjoy, that rarely have waits, are Carousel of Progress, People Mover, and the train at MK. I really enjoy walking around all the lands at MK, soaking in the atmosphere and enjoying the details that make the "feel" so specific depending on where you are. Looking for hidden Mickeys is always fun.
At AK, the jungle trek is awesome!
Epcot, exploring the shops in World Showcase really interesting and fun.
Resort hopping is relaxing and fun. We always start with the monorail resorts, just because riding on the monorail is fun in of itself. There is just more to see, at the resorts, than I can even begin to mention. Even the value resorts have fun stuff to see, and take photographs with, all over the common areas.
Of course there is Disney Springs, and lots of shops there.
My favorite of all, being Fort Wilderness regulars, is Chip & Dale's campfire, sing-a-long, and move every night. It's free and open to guests of all WDW resorts. There is a truck that sells s'mores kits for the campfire, or you can bring your own.