Also note that based on your plan, even assuming you have the right status, you would only be able to have the two kids (assuming one becomes of sufficient age) in the front row of ET if one of them has a status that allows free seat selection or if you pay for their seat allocation. Otherwise, once you split the booking, if the adults are the ones with status, there would be noone with status left in the ET booking and therefore no free seat selection. Even if you are Gold or above, TCP wouldn't work either as it only works for other passengers in the same flight and cabin (ie not to give free seat selection to others in an entirely different cabin).