Hello friend,
Starting a new class and of different language is really a different task.I think they understand a bit English so you can start up with Hello and giving your introduction and then continue your teaching process but after sometime if you you feel that if most of them are not taking interest in your subject then you can start talking with them on any general talking,it will give them time to understand and make them feel comfortable with you.
This way or the other try to make them feel comfortable with you.
Regards,
Nelson