First of all don't take for granted that they can all tell the time from a clock face. It would probably be best to stick to digital. I am guessing that this lesson is being observed. You don't want to find your self side tracked into teaching how to tell the time to some in the class. Make sure that you revise relevant numbers first, good starter activity probably. Dominos are good. Listening activity with times Oral pair work back 2 back. Each student has half the times and they give each other the missing times.