Quick follow up and in line with keeping them busy...
Some things can be done as a large group, but if you have help - maybe you can split them up into groups of two. One group works on dribbling and passing, while another group works on layups and jumpshots.
Mix the groups up - and be smart about splitting them up for scrimmages. Always mix up the scrimmage teams too, yes you want the boys to get familiar with each other, but you don't want 1-2 kids dominating the whole thing - move your power players around and build everyone up.