I put Simon and Hallie in their "condo", it is 2 excercise pens put together and their kennels are in there so they have lots of room to play. In it I put some of their stuffed toys and these ball like things I found at petsmart, they are open and treats fit inside. It seems to keep them occupied longer than the kong toys and they are too big to choke on.
I do this yet I know all they do is sleep when I'm gone but it gives me peace of mind