Coquelet is a nicer word for a baby chicken than poussin. Coquelets are cheap and the implications of this fact need to be taken on board, for there is no such thing as a free-range baby chicken. Even so, you can get a delicious result by marinating them before grilling, which will give you an excellent depth of flavour and a lovely crisp skin. Half a bird per person is sufficient for a first course, while a whole one makes a generous main dish with a salad.
If cooking on a barbecue, be careful not to start too close to the heat or you will burn the skin before the inside is cooked.