While I believe all are basically equivalent, here are the slight nuisances of how one might read each of them:
Planning content - the act of preparing what content or material would be shown
Planning program - a software program that assists the user with planning events or calendar items
Content planning - planning what content or material to present, also implies that such planning is available as a feature of a product
Program planning - preparing a program's items or events. This also has an alternate definition of making a design for a piece of software.
If forced to choose one over the other, I'd probably go with planning content, or content planning - depending on the context in which it is used.