All the hotels offer a buffet breakfast. For the evening meal, most hotels provide a buffet, so hopefully anyone with dietary requirements should be able to select items from the buffet. Please note that they may not have labels for the dishes though or a list of ingredients.
One of the hotels serves a set menu. They have indicated that they can provide for dietary requirements. It's worth bearing in mind though that from our experience, hotels in Turkey don't tend to be as used to dealing with dietary requirements as hotels in the UK. We pass on dietary requirements to the hotel before the group arrives. Please check though with the restaurant staff that they have received this information and that the food you are being given is suitable.
In Istanbul, breakfast is provided at the hotel but not the evening meal, so you will be able to choose what you eat from the local restaurants.
For the flights, Turkish Airlines offer categories e.g. vegetarian or gluten free. You can check the full list on their website. They aren't able to offer specific meal requests that don't fit in one of their categories e.g. vegetarian with no onion. We will choose the category that we think matches closest with your dietary requirement but please let us know if you have a specific request (e.g. if your diet is gluten free and vegetarian you can let us know if you would prefer the gluten free option or the vegetarian option, otherwise we will choose one of these).