Engine Offs to the ground are a must, they are part of the sylabus and not anly that they are the most important part of a real engine failure scenario. What is the point of carrying out a fantastic auto entry, Mayday call, and carry out all the tricks of the trade if you do not know how to land. There should be some safety requirment built into the training so i will not do engine offs in less than 10 kts of wind.
I f there are any doubts about personal competency then see your chief pilot ar instructor and go and practice some for half an hour.
P.S. expect the unexpected from you students.