I have been wearing earing aids all my life, I have one in both ears and I hated the background noise they pick up.
I would say the best way to go is phone the Royal Hallanshire up for an appointment so your Grandpa can have a hearing test. They should provide him with digital hearing aids which are wonderful I have to say. I have been wearing mine for several years now. Also I would not get in-ear ones they are way exspensive plus I know of some people that have them and they can hurt the ears.
I hope this helps.