Just gleaning information.
Budget isn't a big issue for me. Tentative plans are for a deluxe resort w/o concierge service. Location is a factor. We like leaving the park and being in our room shortly after or taking a mid-day siesta.
My initial dilemma was Poly vs Wilderness Lodge. Is Poly $100/night better? Being from the upper Midwest, WL atmosphere is not as unique to us. It seems similar the Great Wolf lodges found around the US.
Is GF too "fancy"? I like wearing shorts and a t-shirt when I'm on vacation with my kids.
Well, there you go, sounds like you've done most of the decision-making yourself!
If siestas are important, I'd humble suggest maybe, just maybe, the Poly would be the best of the MK/monorail resorts, mainly because, while you're on the resort monorail loop, you're also walking distance to the TTC and that monorail. This means you're within walking distance from the monorail to Epcot, AND if you're in the MK and want to get back, you can take either monorail to return to the Poly. Granted, neither monorail should take a hell of a lot of time, but it's nice to have those options. Grand Floridian is very nice, but if you're walking around in a bathing suit or shorts, I assure you, you won't be the only one. Getting slightly more gussied for meals would be nice, but I'm sure you knew that.
An alternate suggestion would be Yacht/Beach Club or Boardwalk. The theming there is vastly different than the Wilderness Lodge, they're within walking distance of each other, AND they're within walking distance (or a boat ride) to both Epcot and MGM. Sounds like you're more set on spending most of your time at MK, so the monorial (or ferry service from WL) would be better, but there's plenty to do at the Epcot resorts for the times you want to get out of the park (and of course, the sand-bottomed pool at Y&BC is the best themed in any of the resorts, almost a mini-water park itself), you have the Boardwalk Midway games and restaurants.
I guess basically,, I stand by my earlier suggestion.
www.allearsnet.com. And get the planning video. Talk to the kids about what they expect the trip to be like (also good for making sure expectations aren't too ridiculous, for anyone), and then you'll probably be able to make a better-informed decision.