I have done loads of this sort of stuff but I may need to stretch my brain a bit more.
One idea is to indroduce the different cultures to each others culture, ignorance =prejudice....make it all fun. An idea is to do some brainstorming,to get an idea of the different cultures, then the leader can divide the group into 5 groups of 4 for example, write on some cards things that have been identified from the brainstorming such as religion eg, Muslim, festivals, such as Easter, Food, such as Jerk Chicken, Music, say Spanish etc etc. get the young people to pick out a card for each group and then plan and research to do demonstate what is on the card.THey can choose to cook something, perform a short role play piece, make some music and perform a dance, make something with craft, masks, divali lamps, poster etc etc or just do a display with articals from that culture such as flags, story's etc. The young people can ask people from that ethnic group, find information on the internet and also from any information in the club (the youth leader should be prepared for that and have plenty of stuff on hand) THe young people can plan what they want to do and perform it the next session and also move around to each others display, this can be made to last several sessions cumulating in a multi cultural "party" with food provided from different cultures, music from different cultures and art from different cultures or done quickly to capture and not loose too many young people!! anyone...MUST go...Steve wants his pudding and the dog is looking at me toooooooo!!