I'd be VERY surprised if a restaurant ONLY served fish. I'm a veggie past 30 years, even when on holidays back in the 80's/90's in other countries at "fish restaurants" it meant they specialised in fish but not that this was all they served.
Was there REALLY absolutely nothing dd1 could have had? Any dish that could have been requested sans fish but still provided a meal?
And if you're completely honest - DO you favour dd1? If she's the fussiest does that mean you're always accommodating her to the detriment of others?
I'd go with taking it in turns to choose as long as the restaurant chosen has SOMETHING everyone can eat.
"Take it in turns to choose. Otherwise the fussiest always gets their way and everybody else is limited." Yes can absolutely see this happening.
And yes - once in a while only getting chips and a salad won't do dd1 any harm.
A restaurant with only 3 options? Nah not buying it - what were the dishes? Also not buying no suitable sides which dd1 could have a few of.
Both more than old enough to be told fussiness for no good reason (oral issues, Sen, intolerances, ethics & religion aside) is ridiculous and selfish.
How old is ds? Could 2 go to one restaurant and 2 to another?
"If he can digest tuna he can digest chicken imo." - seconding the call to tell him NOT to claim he is vegetarian because he isn't, but on the digestion he is right. I have found by happenstance since becoming veggie for ethical reasons that even a hint of red meat or products eaten accidentally upsets my stomach. I was also a geriatric nurse for several years and the reason fish is popular for sick people and the elderly is because it's high protein but easy to digest. It's due to less connective tissue and less fat.
"I know plenty of other ex-veggies who found the same thing." I know plenty who found the opposite - that they had to reintroduce meat proteins gradually working up to red meat. And I've known plenty of people as they age gradually eating less red meat, sometimes eventually giving it up altogether, some who've had to give up on poultry too and become essentially pescatarian purely through digestion & ageing issues.
Lot of people assuming there's another adult - I haven't seen anything in OP'S posts to show that, so op is it just you and 3 DC? So yes, but is Iceland a particularly dangerous place? I'd have thought dd2 and ds (how old is he?) could go to fish restaurant while you and dd1 go elsewhere nearby.
"and only in the last ten years or so I’d say that that view has been revised" nope - I've been veggie 30 years and only rarely have people idiots thought that inc fish.
Mummyoflittledragon - supposedly term for your mum would be flexitarian - but that generally applies to people who keep meat eating to a minimum for environmental ethics.
No pescatarian dd shouldn't trump dd1 ALL the time but I think for ONE meal her maybe just having chips and a dessert won't kill her. Dd1 doesn't get to trump either!
Dd1 won't eat fish or cheese - what else won't she eat? When did the fussiness start and do you know why? It is rather starting to sound like you pandered to perhaps toddler fussiness? Must admit I'm also wondering why you chose Iceland with a child that won't eat fish!
Not everyone who is veggie, pescatarian or even vegan does so due to animal cruelty ethics. Some do due to intolerances, some due to environmental ethics, some have textural issues with certain foods, some just don't like certain foods, sometimes it's a disguise for having an eating disorder.