I would suggest AVForums for some decent feedback but first you need to know whether your father will just watch DVD movies bought from the shop or will he be watching DivX movies too. I bought a Shinco 1720C 7". The Shinco will playback MP3,CD, digital photos, MPEG4, DivX and of course DVD's. Freeview can also be viewed by buying an additional card which acts as an aerial. The sound via the inbuilt speakers is poor TBH although, if it is being plugged into the TV then you have no worries and 2 sets of headphones can be inserted into the portable for dual viewing.
The bag for the player fell apart within month's but I cannot fault the players versatility.
I would expect this to be hovering around the ton mark but the previous incarnation 1720A can be purchased for much less although, it does not support Freeview.
Supermarkets are offering cheap portable DVD players but I cannot vouch for the quality.
Research as much as you can and hold out until after Xmas would be my advice.