Though I'm not a huge fan of Shun knives, that one you linked seems pretty awesome - and even better that your son got it for you.
Wrt filet knives, I've got a nice Rapala knife, but Dexter-Russell is the industry standard, as far as brands go. Anywhere from $30-50 should land you something really good imo.
If you're looking for a boning / honesuki knife, that's a totally different ball game.
Also - your youngest son is 27 years old???