Group Training Assessment
I assume that you are talking about personal training for more than one person at a time and not group exercise.
Frankly, I don’t know why there should be any other assessment than one you would do for an individual. I know it takes more time but you will need to know which exercises to modify for certain individuals in the group based on the assessment. Such assessment will also give you an idea if there should be a person who – based on the assessment – just does not meet the criteria for such group training.