One idea if they will all be teaching different subjects is to break them into groups and present lessons to their group members for their subject.
Let's say you have a group with a history teacher, math teacher, social studies teacher, science teacher and a physical education teacher. Then have the history teacher (for example) teach a short 15-20 minute lesson on history entirely in English. Have the "students" take notes, ask questions as if they were younger students and so on. The history teacher could also give the group a very short assignment, activity or something along those lines.
Before you present the activity make sure the teachers understand that this is a "mini" lesson and to review what they want to accomplish in the lesson. Also, make sure the entire "lesson" takes place in English. Challenge your students to only speak English so they get comfortable teaching with English that way when they are teaching their students they will inspire confidence. If they have to keep resorting to their native language the students will feel less comfortable or able to learn a new subject through English.
Another thing all teachers like to learn are some good games
that use English. Teach a handful of games
to your teacher-students that they can use in their classroom. If possible, do the games with them so they know how fun they can be. Teachers are always looking for fun and engaging activities to use in class.
Lastly here are a few games I have used with university/adult students that you might try: Listening Activity for Adults Two Truths & a Lie Jeopardy
I hope this helps. Let us know how it goes and what worked for you.