A couple of suggestions come to mind. One is, if at all possible, to try to separate out the boys into their own classes by age -- not even level at this point. The difference betweeen a two year old and a six year old is enormous! And, I've found that if you can batch them by age, then the perfect length of class is suggested by their ages: 3, 30 minutes; 4, 40 minutes; 5, 50 minutes; and 6, 60 minutes.
Keep the class moving. You can still alternate active and passive things like you might do for your regular CM classes, but keep it faster paced. Perhaps "heavier" on the active stuff.
Boys love jumping and there are many things you can do: Have them run and jump over mats (you can make this progressively more difficult by insisting they all land on the right leg, or that they hold their arms in a position while leaping, then add that they land with no or little noise, etc.); jump over and run/crawl through boxes; jump over YOU (while you're a lying on the floor; jump over each other. Slides (galops) are fun too.
If you have a portable barre, put it parallel to the one afixed to the wall so you get a set of parallel barres going. Have them push themselves up into a sous-sus position. Insist they get still and have their feet stretched. Add on a sharp open/close of their feet (entrechat), with an emphasis on the opening the legs to the side. Stays in between each one. As they get stronger you can add more beats. Lastly you can have them bring their feet up to the front, so their bodies are making an "L" shape. Boys LOVE this exercise.
Wall push-ups are good for boys, in addition to sit-ups, curl-ups, and regular push-ups.
You can tap ("re-direct") all their wonderful energy and make it a fun and positive experience -- for them and for you. Best wishes!