What year group are they? Would a rice salad be suitable for a Carribean theme. Either dem how to cook the rice and have it ready cooked for them to use. Or if plenty of adults around let them work in 2s and cook their own rice and prepare the fruit/vegetables to go in it. Could use peppers, pineapple or any other fruit and veg you wish. Very lightly coat it in either salad cream or natural yogurt. I have done things like this in the past as part of our induction programme. The key to making it work is have everything ready weighed out and the equipment to hand. You need plenty of adult supervision/help as you and the room will be new to the pupils.