You probably won't even read this response because you believe I was jumping all over you and being snarky or whatever. That's fine. I tend to speak honestly and bluntly. Take it or leave it. I don't like when people are wishy washy and fake nice and don't just come out and say how they feel. My delivery is probably not the best, but I assure you there was no nasty intent.
For what its worth, my only 2 children are also autistic. They are older teens now. It's been a long ride with lots of bumps along the way. Like your kids, they are also very logic driven. To them, even as young toddlers, pajamas are for sleeping, period. They never wanted to eat anything in pajamas, ever. They would wake up and immediately get dressed, and still do to this day (ages 17 and 19 at this point). I have tried to tell them they can eat breakfast in their pajamas if they want, and they look at me like that's crazy talk.
So, I mean, all kids are different, definitely, but there is a very real opportunity to just establish "the rule" that "we get dressed to go in public places with other people around." My kids are ALL about guidelines for things. I think it helps them to just know straight up what is expected of them.
Autistic people struggle mightily with making inferences and trying to figure out social norms on their own. You have to teach them literally everything about how they will be expected to behave and present themselves in different environments and situations. And they will listen and apply whatever you teach them forever, most likely. So take the opportunity to model what will be expected of them when they are adults out in the real world on their own one day. That's my free advice for parents of young autistic kids. Again, take it or leave it, but it meant to be helpful.
My kids are also boys who have always showered at night right before bed, so getting them dressed in the mornings for breakfast on vacation was literally a one minute deal. We would lay out the clothes the night before and either dress them ourselves when they were very little, or they would do it immediately upon waking themselves. Sometimes it was easier for me to grab some breakfast and bring it back to the room, but even then, they would be dressed. We had to make the decision whether to take them into the lounge each morning based on how well they slept and how likely a meltdown would be if they accidently spilled some milk or something. Because we DID have the fun experience of a meltdown in Cabanas when they ran out of bacon and we had to wait 10 minutes for more (guess who didn't even get to eat that morning?) and once in a concierge lounge when one son accidentally knocked over his water and ONE DROP landed on my youngest. That one was so bad that we had to basically go back to our room for 3 hours to get him calmed down again and we missed out on our morning plans. So, if your kids are prone to moody mornings, best to just do as much as you can to provide a controlled situation in the room. Room service breakfast sounds like a lovely compromise.