4 weeks?  I don't think you can travel around with them everyday..... If they dunno English, I guess you will need some Chinese DVDs or even a TVB satellite channel to entertain them 
 
By the way, some nice museums in London are free of charge.  Or, you can make a short trip to Europe.  Try to have a look at the websites like www.eurostar.com or www.lastminute.com
  
    
 
 
 
 
 
ALL ANIMALS ARE EQUAL, BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS.