How big is their coop (at least 12 square feet)? How hot will it be during the day? Can you provide a small fan for extra ventilation? Can you absolutely secure that dog kennel to the coop opening so it canNOT be moved? Throw in a head of cabbage and a whole cantaloupe or such, scatter a good share of scratch grain on the floor, and they'll be perfectly entertained.
From the description of your setup, I'm more concerned about security from predators while you're away than I am about space and activity.