We learn so much from our parents and grandparents through their entire lives just by watching how they deal with the trials, tribulations, and small triumphs in their lives. They continue to help us grow as a person even after their passing.
Good on you Mike for helping your grandfather. You are not only helping him but yourself as well. And your kids - they are watching and learning through all of this. My own son never knew his grandfather to be anything other than incapacitated and unable to speak due to a stroke. Because of my dad's condition my son never had a chance to have a real relationship with his grandfather but that didn't mean that my dad wasn't in some way contributing to my son's development.
When my son was about 12 he suddenly said to me "Your dad must feel extremely proud to have a son that helps him like you do." I was and am extremely proud of my own son for thinking that and I recognized perhaps for the first time how each and every member of one's family makes us all better in some way.
Watching cherished family members get old and sick is not easy but a lot of good comes from your helping your grandfather through this.