@drtroubles - I think that getting your dad a hook threader would be a great gift. My uncle uses a knot tying tool as well as a threader, and it really helps him get through his preparation work quickly. I would look into any and all kind of assistance tools you can find.
You can find fly threaders and fly tying tools too, if your dad does any fly fishing. I think the best idea would be for you to go into a reputable fishing supply store and tell them the problems your dad is having. They should be able to get you set up with all of the tools you will need to get your dad threading and tying hooks again.