Hi! I just read your post and I think that the answer also depends on the age of your pupils!!!
I teach in Primary School and I only use English in some classes of very young pupils because I think that this resembles the way they would have if they went to another country! They would be forced to get the language and everyone says it's the best way!!! It doesn't matter if they don't understand everything! They will eventually! Everything will fall into place! Of course you need to go slower but in the long run it will be better. As for translation, I give them the meaning in their mother