You'll get as many different answers to this as you get answers. But my opinion is follows:
I've only done "Adult Trips," both solo for business and with my wife. If I was going to be there, I'd do the following (and why).
Friday, Magic Kingdom. Saturdays are just a no-no, in my book, at MK. Too crowded. Even in September, when Disney is at a crawl, MK is crowded. Sunday's MK early entry day, which could make it a bit nuts, too. And Monday seems to be historically the day a lot of folks head to MK that are coming in for a week. So Friday is your best bet, in my opinion.
Saturday, Epcot. While nothing is uncrowded on Saturdays in the world, Epcot seems to be the best bet. It's the biggest park, and in my opinion has the most to offer those doing an adult trip. Most of the best eating and drinking is there, and World Showcase will be mild even on the busiest day because it's not really an area that hold small children's attention. Note: Saturday is MGM EE.
Sunday, MGM. Same deal on weekends with MGM, but no EE on Sunday. Some folks can spend a week in MGM. I can only spend a short day there. So I'd go back to Epcot at the point where I need a change (assuming you have hoppers).
Monday, mop up day. AK is the EE park. Hit MK early in the morning if you want some more. Otherwise, indulge. I notice you didn't have AK on your list, but if you thought about going there, Monday is their EE. We always use the last day to visit MK one more time, then just laze around Epcot. There is so much to see in the countries. And again, it's the most "adult" park there is. In addition to food and beverage, there's lot's of films (like "O Canada," a 360 film that's not to be missed), lot's of street theatre (be sure to spend some time in the UK Pavillion), and shopping that's lot's of fun whether you're spending money or not.
This does not take into account EE if you're at a WDW eligible resort. If so, that may change your plan. We avoid EE, whether we're on site or off. Some would argue with that, but again, you'll get multiple answers to your original question.
And by heaven's, if you're going on an adult-oriented trip, get thee to Pleasure Island and spend an evening in the Adventurer's Club!
Enjoy,
Pat
