Give them a bit of the soup over extra cous cous if you have any left? Give them the soup - but have fish fingers ready? It won't hurt to give them ff for once, will it? And you don't want to give them a reaction against spicy food - you know what kids can be like!
Coconut milk is supposed to reduce spicyness - not something everyone would have in their cupboard as a matter of course, but perhaps a useful "just in case" think to have lurking. You can get it in cartons with a very long shelf life.