I had bariatric surgery and while I do not eat quite keto, I eat low carb. And I pretty much 'ate what I want' on my disney trip, but what I wanted was mostly low carb with a few bites of treats here and there.
They will substitute sides freely at all TS restaurants... even at a signature, if you look at the rest of the entrees and find something you want more, they are happy to sub. So find two interesting veggies and go for it. My son got the filet with the mac and cheese side from another entree at CA Grill and they did not bat an eye.... of course that's carby but you get the idea.
I'm sure you know this already but be wary of "no sugar added" desserts as they are packed full of carbs, and even natural sugars, just not any additional added.
I stuck to my "eat mostly protein and veggies" and did have a few bites of starchy food (like the ear off of a mickey waffle or a couple of tater tots) and the taste was enough for me, it did not set off any cravings. But the bulk of my meals were protein and veggies.
I eat so little I never worry about condiments and sauces because I'm so portion controlled (per my nutritionist). If I were on vacation though, I still would not worry about it if my goal was to maintain more or less my normal style of eating vs. staying strictly in ketosis... but that's just me. YMMV.
Satu'li Canteen is a dream come true, I found the salad base delicious.
There are salad options in all of the parks, maybe not at every QS but at lots of them. At MK there is Pecos Bill's, Columbia Harbor House (which also has a salmon entree you can get with double veggies) and Cosmic Ray's (you can also get a roasted chicken at dinner, sub more veggies for mashed potatoes). At Epcot, Sunshine Seasons has tons of options... besides salads, there is the grill and you can sub double veggies for the starchy sides with your chicken or pork chop... they will let you have anything at that station but won't go to another station. Eating around the world is a bit harder but I think France also has a nicoise salad and the ice cream macaron was actually one of my planned indulgences (and worth it). Also Liberty Inn at the American Pavilion has a new grilled chicken cobb salad that sounds quite good, I'd be all over that (I know, boring to eat THERE but hey). I find most of world showcase to be pretty carb heavy... everything has a lot of rice or noodles or chips or bread. I don't know if they will substitute more tabouleh for couscous and you can skip the bread...don't know how you feel about hummus, I eat it and beans (which is part of my "low carb but not keto" because I can't eat it in quantity to get a ton of carbs in.) In HS I never eat QS but I know that Backlot Express at the very least has a salad option. We didn't go to HS this time. If I was traveling without kid and wanted a lunchtime salad I'd go to the Brown Derby Lounge and have the cobb.
Buffets are of course easy but I'd doublecheck the menu, something like Trail's End might not be as meat/salad/veggie heavy as some other choices are (with things like fried chicken and bbq featuring heavily). Breakfast buffets are super simple to eat low carb if you can resist the temptation of the carby stuff (I had a few bites with every breakfast, I admit!) But there are tons of egg options (usually premade eggs and some kind of frittata and some have made to order eggs/omelets) and plenty of breakfast meat... most of them have some kind of grilled veggies too if I remember.
Snacks are tougher but there are some veggies and ranch dip and babybel cheese options out there. Most of the snacks are things like ice cream and popcorn and fruit even as healthier choices. but honestly if you eat decent meals you won't NEED to snack and then it can be a choice to treat yourself if you wish.
Anyway that is kind of my go-to stuff. I was exactly the same weight when I came home (I was on a cruise too and ate significantly worse there) and within 2 days of being in the bathroom nonstop had peed out 3 lbs, so it all worked out. Hope it's helpful!