Sleeping in sounds relaxing in theory, but what you are really doing is guaranteeing that when you arrive at the parks, it'll be hot and crowded. We much prefer arriving early, having an early TS lunch in the park, and then heading back to the hotel to chill by the pool to avoid the peak early afternoon crowds, before returning for the last couple of hours at the park once people have started to leave for dinner.
I second what others have said about splitting up. I've often taken the kids on a ride or two while DH sits and reads a book at a coffee shop or lounge. He also sometimes joins us at the park later in the morning or leaves after dinner (or used to, before the reduced hours). With cell phones, it's never hard to fine one another, and it gives him an opportunity to check out and kick back a bit, while we go on the rides with the longer lines or that he is not a fan of.
Like others have said, I can't think of anything less relaxing than all QS meals. While some people love mobile order, we find it frustrating to navigate, time-consuming, and often glitchy. And once you are there, you have to stalk tables for one to open up, carry a loaded tray (with no lids on drinks any more, not always the easiest), and clean up everything when you're done. None of it is world-ending stuff, but such a different experience from unwinding at a TS restaurant. Get same day ADRs or do walk-up waitlist for TS, and you can also eat at lounges which are always no-reservation.
The one thing I do agree with is the plan to hop to Epcot in the evening. Epcot is always lovely at night, and Boardwalk makes it super convenient. Highly recommend catching Mariachi Cobre in the outdoor theater near America pavillion. Perfect place to unwind.
That was pretty relaxing. We swam, swam, swam and swam some more. We also did pony rides, bike rides, and visited a few other resorts.
