We usually took some frisbees, a playground ball, and some cones to family campouts. As the BALOO trained organizer, I didn't plan down time, I planned unstructured time. The campout was generally advertised as a relaxing family activity with a few structured things like a hike or GPS geocache. I let people know that I would bring some frisbees and a ball and encouraged them to bring their favorite game. Remember, this is a FAMILY camp out, not summer camp where every minute of the day is planned from morning to night. Families should take responsibility for themselves and you shouldn't try to plan out every hour for them.
"Dinner is probably burgers or hot dogs, dad grilled, so not much involvement from the Cubs."
If Dad grills the dogs, you miss a great opportunity for the kids to have a valid reason for holding a stick over a fire. Let them cook their own hot dogs - they'll love it! I didn't allow boys to play in the fire, so cooking hot dogs was a way for them to interact with the fire.
As the BALOO trained leaders for the pack, you should be in charge of planning and they should be listening to you. After all, you went to the training and understand the purpose and methods of the pack family campout. With the exception of Webelos leaders who can take their dens camping by themselves, the other den leaders should be checking with you because this is a PACK family campout, not a bunch of dens who happen to be camping at the same place. Even the Webelos leaders should be working with the pack on a pack campout. Now, there is nothing wrong with having a specific den responsible for coordinating an event for the pack. The difference is that everybody who wants to will participate in that event.
My pack would provide breakfast on Sunday morning as a fun/nice thing to do. After a couple times of watching people pack up, eat, and leave while I was stuck cooking and cleaning up for them, I decided that the combined meal would be Saturday night. That seemed to work better as people were more willing to help with cleanup and I didn't feel like I was stuck in the kitchen the whole time. It was kind of a self-inflicted struggle because I wanted to expose people to the broad possibilities of Dutch Oven cooking, but that was often in sharp contrast to the people that brought their pre-packaged no cook meals. After the switch, it no longer bothered me when people packed up while I was cooking because I ate gourmet food while they ate their cold whatevers.