Work on keeping their necks up at a 90 degree angle to their backs. This will improve the appearance of their profiles and help them to brace more effectively.
For the clippers, I really am not a fan of the Osters. They are too big and hot and heavy. I personally like the Premiers, but for younger showman, Lister Stars are probably the best. They use standard size blades but are small enough that you can use them on the faces too. Surgical blades for the body and fines for the head.