Just here to add that Garden Grill is *highly* recommended by our family! It is one of our most anticipated meals and a "must do" at EPOCT every time we visit.
Our (adult) daughter and I are (in)famous for sneaking off to Disney World every January (including this past one) for a couple of weeks to play and have fun, and go shopping, and drink Adult Beverages! We typically try for 2 trips per year, but for 2020 I think we will be lucky to go again this coming January...
Back to Garden Grill! If he rides "The Land" prior to eating at Garden Grill, he may see some of the very foods being grown that are in your meal! (Not to mention, it's just a neat little boat ride!
The loveliest part of all is that (for us) the entire dining experience takes about 1 rotation of the restaurant. It is "all you care to eat", but instead of a traditional buffet line, the server will bring out more of whatever you want. If there is something on the skillet that you know neither one of you will eat, you can also tell them to leave it out so the food won't be wasted. The service there has always been wonderful for us, and the food is fresh and very tasty! There is one section (as you rotate back around to the front) where the animatronic dog from "The Land" can be heard barking over and over, however, it doesn't happen suddenly - you hear it as you come around, and it gets louder, but it is rhythmic and repetitive, and does not happen suddenly. Remember that the Garden Grill sits directly above The Land ride, so it kind of reflects the ride underneath! It is not dark, or dim - it is "regular" lighting. The characters tend to be Mickey, Pluto, Chip & Dale, and the interactions (pre-COVID) were always tableside, and you could take selfies with them, and they would sign autographs. Chip & Dale especially would create fun interactions where they might "steal" a waiter's tray or some other fun distraction, but it typically was not noisy per se. I don't know how they are handling the characters here now; I presume you won't get the interactions that we saw before the pandemic, however.
At EPCOT we also like to dine outdoors (even in January) at Katsura Grill in Japan/World Showcase - there are 2 outdoor dining areas as you walk up on the ramp side, and often there are Disney Ducks that like to "visit" the diners who sit outside on the patio just outside the main doors! It is very peaceful up there, with waterfalls and koi ponds, and the food is my personal favorite meal at WDW, every time, hands down. I try to sneak in at least one lunch and one dinner there to bookend my trip! The interior of the QS itself brightly lit, but the outdoors section has both sunny and shady areas. In "normal" times, the lower terrace is very popular just before fireworks; the upper patio outside the doors has a more obstructed view of the lake.
The Plaza at MK is an excellent choice - and another one of our family's "must do" dining spots. Our (adult) daughter has to have her birthday lunch there every trip, or I will never hear the end of it; we have pictures of her birthday lunches there every year going all the way back through her childhood! Standard lighting here, but not as bright as outdoors certainly.
At Hollywood Studios, PizzaRizzo might be a good bet - typically upstairs (if it is open) is quieter than downstairs, and there is an elevator. This past January, we spent an lovely, relaxed lunch there; we sat up on the second floor for more than 45 minutes and just relaxed after having some pizza! Again, standard lighting, but there is one side where you can sit away from the windows and it feels less bright. If he likes Star Wars, Ronto Roasters may be a bit of sensory overload but it's a lot of fun! Docking Bay 7 is also in Galaxy's Edge, and while it doesn't have a lot of loud sharp noises, if it is crowded with other Guests, it can feel noisier. It is *very* immersive, and we felt like it represents some of the best theming we have seen at a Disney QS ever.
Animal Kingdom has very little open right now that I would recommend; that might be the day that you find a QS you like, and then a warm, happy little corner somewhere to dine al fresco!
At Disney Springs, I can highly recommend Wine Bar George (yes, they have food, as well as Adult Beverages); it tends to be quieter and more chill than the average Disney Springs table service restaurants, especially mid-afternoon. It is darker inside on the first floor in the daytime, the second level is brighter; we tend to stay downstairs simply because it is closer to the wine! Moriomoto's is fantastic as well, but try for a late lunch/early dinner seating there; the later in the evening, the louder the bar area gets. It is not dim, (there are floor-to-ceiling windows) but is again less bright than outdoors, and you can sit towards the back, where the high banquettes will help block some of the light and make it quieter.
From what I understand, Oliva's at OKW is not currently open and serving, but if they are in January, it is such a lovely, relaxing, peaceful place. As with all of our favorite places, we tend to run by there for either a late lunch/early dinner when it's very slow, and so have been spoiled, both by the food and the waitstaff
If you are able to get over to Wilderness Lodge (short boat ride from MK) you will find that Roaring Fork (the QS inside the Lodge) as well as Geyser Point (the QS that is lakeside) are both relaxed and pretty easygoing. Geyser Point can be a bit noisy if there are sporting events on TV, but that is typically later in the evenings. Because it is open-air, it can be bright in the daytime. Roaring Fork has an expanded outdoor patio that is shady and quite lovely even in January (quartz heaters in the ceiling bathe you in warmth) as long as it isn't too windy or rainy. There is also a small dining area indoors for Roaring Fork, and it is not as bright as outdoors; going between meals you will often find it nearly empty.
So many of the places that I would normally recommend are currently closed; we have already decided that if we do try for a January trip ourselves, we will likely breakfast in the room every day, just to have one stress-free meal. Probably the hardest part right now is knowing what will/won't be open in January - we already know that things will likely still be quite different than normal, and a lot of our favorites will be closed. One of our strategies on days when one or both of us is just feeling overwhelmed by the "Disneyness" of it all is for one of us to grab a QS meal while the other one holds a spot (outdoor dining table or bench) and we purposely look for areas that are less busy, so it's often the tables that maybe don't have the best view, or are a bit further away, but you get the peace and quiet to enjoy your meal and refresh!
I don't know what DoorDash and UberEats are doing in Orlando right now regarding deliveries to Disney World - it may be possible that you could order food delivered to your room at OKW from some of his favorite chain restaurants as well.
I hope you all have a lovely trip! I so enjoy running away with my daughter every year to Disney World; it's become a cherished tradition!