First the size of the TV depends on how far away he's going to be watching from. He'll be 10-12' away from the screen, so a 60-65" TV would be best. Next he needs to consider how much ambient light there is, and if he can darken the room. He has a lot of sun coming in, so Leo recommends an LCD TV. The Plasma TVs aren't as bright and reflect light more.
For a good middle of the road, value brand, Leo likes Vizio. This is a very good option for less money than some of the bigger brands. He should definitely look for an internet connected TV, and that it's LED backlit.