You sound v nice OP so please don't take this as criticism! Because it's really not.
In the end I think you are being reasonable and also v nice to cook, tell them what cooking to see they liked it etc.
The reason I think they are also being reasonable. Well maybe not totally because they could have said something. But then you could have as well I suppose! But on hols one other family naturally you don't want to risk anything that might turn Atmos uncomfy!
Anyway I've been on hols after children twice with friends and their families. And I'm never doing it again. Because different families often have v different ideas about hols in really fundamental ways.
First was with about 4 other families all women friends since school, all men lovely and get on, children all nice and friendly etc.
The relevant one is when went on hol with best mate since school. Our partners both nice and get on. 4 kids all mates.
Thing is we're really random on holiday. Don't plan to do this or that. Eat at random times. Get up late. Some days let's bimble around and some days right let's do X outing that we have decided looks good. Might have big lunch out and only want easy for supper. Etc.
They were planners. And stuck to plans. And would inform us of the plans with expectation we would go along with it. Timings. Then.. we like walking a lot on hols they weren't interested. They liked meeting for X time for breakfast we didn't. Obv we walked and they breakfasted without us early.
It was just a real mismatch of norms generally and holiday approach.
Anyway we're still close friends but we've never mentioned that hol again!
So my guess, just a guess is they are more do whatever feel like esp on hol and found your v generous and tbh normal thing of eating at X time together every day just... Like a fixed must do iyswim? That is not what holiday means for them.
Forget about it, just one of those things.. Don't let it affect your friendship. Don't holiday with them again obv!