Grouping animated objects I've animated a box to open.

In the Dope Sheet the box sides appear as seperate objects, the actions are also seperate. I want to be able to combine the sides in order to export the box as a whole, as some of the animations rely on their parent transforms. Is this possible?

As a side question, what steps can I take to avoid this in the future?
For a pipeline friendly way to solve this problem, I would use an armature to rig the box and then combine the box and rig into a Group.

Then in another file you can link the group, make a proxy of the rig and constrain other scene objects.