If British White are the only ethnic group attending that's what you can focus on
Have you a fair, fete or local carnival that's due or maybe just been held ? You could combine your Children's culture with Jamaican Children's and also look at the Carnivals & festivals that they experience.
As a craft you could make streamers on poles or maybe junk modelling floats. There are quite a few books available for story time & for positive role model images ..