If they want the same image height, they will have to get at least a 32" LCD/Plasma (yes, Vizio makes a 32" Plasma). $299, not going to happen.
I'm assuming that they have OTA only? Before wall-mounting they should ask themselves the following.
1) Where am I going to place / store my DVD player, cable box, receiver, etc?
2) What height do I want to mount it at?
3) Will the comfortable viewing height work in my room? (Mounting above a fire place is almost like sitting in the front row at the theater)
4) How will I hide the cords going from my devices to the TV (I.e. video cables, antenna cords, audio cables, etc)
5) Do I have the knowledge (or willingness to pay an electrician) to properly mount an electrical outlet directly behind my mounting point? (Yet more costs)
More than likely they may decide that using their current stand will be fine. At which point you can explore other HD options (I.e. Tube CRT (Sony had a good 34"), less expensive rear projection).
If the $299 is the budget, they will either give up size or need to wait a few years.