The sentinel rules note:
Standard Actions: To take a standard action, your animal companion needs you to take a standard action to command it to do so.
Thus, the action the character is taking is "Command animal companion to take standard action." not "Express an arbitrary standard action through an animal companion." Just as the animal companion cannot be the source of your druid invocations, as sentinel/druid powers cannot manifest from the animal companion because:
Your animal companion is considered an ally of you and your allies. It can be affected by powers in the same way as any other creature can be.
Therefore, the fact that it is an ally means that the charge originates from the ally, not from the commander of the attack.
Of interest, however, is if the wolf can then be commanded to take actions subsequent to the charge:
- No Further Actions: The creature can’t take any further actions during this turn, except free actions.
Therefore, the creature, the sentinel's ally qua animal companion, cannot take any further actions. The druid therefore can indeed command the animal to take further actions, but the animal cannot act on those commands, and so the commands themselves are all kinds of pointless.