There's nothing more irritating than a bad trigger. An Excaliber Vixen is light and has one of the best triggers. Next year you can have an accudraw installed on the bow and he'll feel more independant or not install it and hunt with you all the time. Donno how much a Vixen is there but the bow, some arrows and broadheads have got to be close.
I think for your dad you won't need the durability of a Vixen so another bow should suffice. Other than the obvious weight ask him how he likes the trigger. The quality of most bows will be good for just hunting. You don't need an Excaliber unless he becomes an arrow junkie like The Squirrel, Dan or myself. We (and others I am sure) shoot hundredn and hundred of arrows a year. Us Excal owners just replace strings once in a while while the other will need some maintenance from time to time. If you are just hunting with the bow and practicing just for hunting you won't need maintenace for quite a few years. That being said, check them all out!
Hope this helps.