Neither will accept sandwiches or toast as an evening meal.
sorry, but you really sound as if you are running a cafe.
My kids do not get to choose dinner! I decide what we are eating. If it is ds favourite, then dd2 is a bit meh, but tough she eats the bits she likes (ds likes lots of meat, dd2 doesn't like meat much)
If it is dd2s favourite meal, ds is a bit meh. I make sure there is somethign they can eat, so plenty of veg for dd2 to fill up on with a tiny peice of meat, and plenty of garlic bread when ds only wants a small portion of dd2s pasta dish, but basically, one meal, one dish, eat it or go hungry.
Stop pandering to them!
I was about to cook something when dd2 whined she didn't want that, she wanted something else. Dd1 whined she didn't want that.
Why did you change plans? tough shit I am cooking xxxx. No I am not cooking something else, that is what is for dinner.
And while I get that it is easier to shop without them, at their age they should be perfectly able to go round a shop, possibly even HELP you shop. So if they are that bad, you need to start taking them and teach them how.