I suggest art projects. Students are very occupied when they are being creative, and keep the materials cool, but simple, so that you don't have too much to manage.
Instruct the kids on how to get the mateirals, how to use them, and how to put them back (this can all be done visually since language can be an issue.)
Games with 30 are likely to be a bit crazy, but old good ones, the same ones one would use for curriculum classes, would work well (like pass the ball in groups, relays, etc.)
good luck!
amy