As others have noted it says in 61.57 that you must be the sole manipulator of the controls for a landing to count for currency. If you were not the sole manipulator of the controls then I would not log the landing. If I need to keep track of the number of landings my students do, I write it in the remarks section of my log book. I generally only do this with presolo students. I do not feel guilty occasionally taking landings from my students, you only need 6 every 90 days, so it is not a big deal.
As far as getting cross country time, if you are a CFI you do not need to log a landing for it to count. If you look in 61.1, you only need to land an an airport 50 nm away for private, instrument, and commercial ratings. So, your student needs to log a landing but you do not. Since you must be an instrument rated commercial pilot to be a CFI, you only need cross country for the ATP and no landing is required. It must only be to a point 50 nm straight line distance from the point of departure. You do not even have to go to an airport.
As a side note, if you want that 135 job and need 1200 hrs and 500 hrs of cc time, it does not have to be 50 nm away. Part 135 cc time is any flight time that includes a landing at a point other than the point of departure. I am not sure if you must log the landing. If your student flew the plane and the flight "included" a landing, I would think that it would count if you recorded that a landing occurred in the remarks.