Don't overthink it if you are going to accept them all anyway. Accepting revisions when there are no revisions is faster than testing to see if there are revisions before accepting.
Code:
Sub AcceptCCTracks()
Dim aCC As ContentControl, aRng As Range
For Each aRng In ActiveDocument.StoryRanges
For Each aCC In aRng.ContentControls
aCC.Range.Revisions.AcceptAll
Next aCC
Next aRng
End Sub