View from the passenger's seat
A big catalyst for automobile/airplane motion sickness is looking down for a while and then looking up.  Let me provide a true story to illustrate this point.  A buddy of mine was traveling on a private jet.  He'd been reading a book for some time and then took a glance out the window.  Although he had never had motion sickness before, he knew he had it now.  Unable to find an air sickness bag, he threw up in his briefcase.  Needless to say, all the other passengers moved away from him.  

Another advantage to having the TV off the floor is that the passengers in the back seat don't have any trouble viewing the screen.  One of my kids tested the system out and found they could view the screen easily from any passenger seat.

As I said earlier, the cup holders are super size to accommodate large drinking cups or mugs with handles.  My biggest child tested exiting the van from the back seat and found there was more than enough clearance for legs.  This photo also shows the ratcheted tie-down holding the TV firmly in place.