Would it be weird, or frowned upon to eat at a TS, but bring in food from a nearby CS restaurant for one (or more) picky kid eaters?

To say that my kids are picky is an understatement of epic proportions. They are both on the Autism spectrum and have major food limitations, which usually get worse on vacation. However, it ends up that what one son likes is always completely different from the other son. When one TS restaurant kid's menu has an item one kid will eat, it usually also doesn't have an item the OTHER kid will eat. For instance, one son likes mac and cheese and pizza. The other only likes hamburgers and chicken tenders. Rarely will I find a kids menu with either burgers or chicken AND either mac and cheese or pizza at the same time.

I want to eat at a couple places where the kids' menu (and even the regular menu) won't be able to accommodate both kids, so I was thinking I'd be able to grab something for one child prior to the meal and bring it in. I'm thinking of this for Whispering Canyon Cafe, since I can head over to Roaring Fork just after we sit down. Or, we could maybe just stop there first, have our kids eat, and then only order them dessert at the sit down meal? What would be acceptable?

We are not on a dining plan, and I know that I could speak to them about special dietary needs and all that, but we don't have ADRs made, and we really don't need "special" meals, just usually what they DON'T have at the restaurant.

I wish they'd standardize the kids menus and offer all the same options everywhere. It would make this so much easier!