This sounds like a very interesting task; I hope you will be able to get the job in the teaching centre.
You are right to say that the teachers will need phrases to manage lessons. One idea for presenting this language to your students is to have the words within the phrases jumbled up. Students reconstruct the phrases. You will then need to do a lot of pronunciation practice; then you can ask each student to take the role of teacher and give instructions to the others in the class. I think you should keep this language visible in the classroom at all times, you or the students could make a poster that is pinned on the wall. Make sure you use this language yourself in all classes.
Your students will also need a lot of practice with oral English. Make sure you give them plenty of opportunities to speak and do a lot of pronunciation practice. They will also need to practise asking questions. You should also do some work on language of praising, encouraging and how to point out errors and areas for improvement; e.g. very good, try again, that’s not quite right…
It would also be a good idea to do spend some time on presentations. As they are experienced teachers, they will know about presentations, your role will be to give them the language to do it in English. They will need a lot of practice with this. Each of them could do a 10 minute presentation of something they are likely to teach. Other students in the class can then give feedback, focusing on positive points and areas to improve. This will also be an opportunity for them to practise the language they have studied.
They will also need vocabulary that is specific to the subject they teach. You can ask them to suggest language they will need to know and prepare worksheets for this. You could put the students into groups according to the subject they will be teaching, to allow them to work with others who will teach their subject.