Hello I prefer to eat either a cauliflower curry or a sweet potato curry. I don't count in any exchanges for both of these but would for the potato part so for example 2 exchanges of potato would be the total amount. For the other parts of the curry such as the spices, herbs and sauce(made of tomatoes mainly) I don't count the exchanges even though tomatoes in a sauce form has quite significant protein.
I wouldn't advise you to eat any of these meals in a takeaway place because you just don't know what goes into them. For me personally, I wouldn't and would rather cook it as I know what I should and shouldn't put in it. If you were going to decide to have some, I am sure a small amount wouldn't do much harm depending on the number of exchanges that your children are on. You can always check with the chef if in doubt and pretty sure he/she could tell you if theres anything in particular that wouldn't be allowed in high protein such as cream added to curry or type of noodles in a chow mein. This probably would be something like egg noodles rather than rice noodles which has far less protein. As I said earlier though, if your children can tolerate a lot of phe in the diet then it shouldn't be a big problem at all.
With the sauces, it's best to stay away from anything with a lot of cream or cheese in it. I suggest a tomato based curry would be ideal with a good deal of vegetables but be careful with some of these as the following have significant protein. These are included in the PKU exchanges book. Also these are helpful for exchanges on various foods and drinks.