As far as resorts... I have no clue on that part, sorry. The restaurants I
can help with though
The best bet would be to take a look at the menus and find stuff that you'd both eat. Note that menus can, and will change, but the basic outlines remain similar. The vast majority of restaurants are not all that fancy at all, while only a select few (really a subset of the signatures) are a bit more upscale.
Some of my favorites, keeping the OP's stuff in mind (pfft, it's almost 4am here so my brain isn't quite running fully

):
Epcot/Epcot Area (YC/BC/Boardwalk):
San Angel Inn, Hacienda de San Angel, Via Napoli: The first two are located in Mexico (hey, I have a think for Mexican, what can I say) and are a bit more low key than the average Disney restaurant. The food is great at both as well. Do check the menus first though, as they are not your typical "Mexican" restaurants and serve a bit more traditional type of food. I also prefer San Angel Inn's lunch to their dinner, but that's mostly just based on the menu offerings and me being so darn picky. Via Napoli is located over in Italy and has some great brick-oven pizzas. Very thin crust with some char on them, so they aren't your typical Dominoes/Pizza Hut style, it's a bit more reflective of actual Italian pizza. It can get a bit noisy though.
Over at the boardwalk, I love Flying Fish Cafe. While it's a signature, it's not as formal as some of the others. It's very good and well worth a trip over to the Boardwalk.
MK/MK Area (Poly, GF, Contemporary):
Inside the park, my two favorites are The Plaza and Liberty Tree Tavern. LTT is a bit more lower key than The Plaza, which can get a little noisy, but both have a bit more simple fare and will more than likely appeal to your more simple fare liking other half. I do prefer lunch at LTT over the family style dinner, but again, that's because I'm weird and picky.
AK/AK Area (AKL and AKV)
I do like Tusker House's breakfast, but it is a character meal and thus may not fit your needs. Nothing else inside the park interests me, though I hear good things about Yak & Yeti. Of course, the whole pickiness thing comes up and ruins it for me!
Both Boma at AKL and Sanaa at AKV are very good though and you should certainly consider them. The menus are a bit more exotic, but not so much that you won't find something you like (unless you only like hot dogs, but if that were the case, you'd not be looking for restaurants, you'd be eating at Casey's

)
DHS/DHS Area (BC/YC/Boardwalk)
Inside the park here, I enjoy Mama Melrose quite a bit. The same outside the park ones here for Epcot.
Misc?
I don't do Downtown Disney, so no input there. I'll give props to Maya Grill though for Birdman above. Had 5 meals there in the past 3 years, and only two weren't that great (both in 2010). Of course, the breakfast was likely my fault, since I don't eat eggs (yup, picky). The dinner in 2010 was just one of those things that happens from time to time (overly bland entrees with very slow inattentive server), both dinners in 2009 and the one in 2011 were very good though.
ETA:
If it's just fancier food that makes him uncomfortable, look into both Artist Point (Wilderness Lodge) and Yachtsman Steakhouse (Yacht Club). Both are signatures and a little more upscale than the norm, but the food is far from over the top and is very good.