A few things.
Get your Cub Scouts each a Balaclava just for sleeping in. Make it loose fitting. Balaclavas tend to work better than just a typical watch cap, as those usually come off as you sleep. You lose a bunch of body heat through your head, so cover it. Dry it out during the day. Don't use the same one during the day, as you do at night, since the one you use during the day will have absorbed a bunch of moisture from use.
Plus have them wearing very large, oversized socks when they are in their bags. All their sleeping clothes, underwear needs to be loose fitting.
Before bed, take a Nalgene bottle and fill it full of hot/boing water and put it in the bottom of the bag. This will help a lot with cold feet. A second one can be used around the core of your body.
Get them each a pee bottle so they don't have to leave the tent. If the temps are very cold, sometimes it is pretty hard to get warm again, after you have gone outside, so stay in the tent.
Hope some of this helps.
Pee bottle for kids? They don't pee often like we old fellers!
