I think you should get a job as a helper first. By helping your grandpa cook, your grandpa will get used to you being busy in the kitchen and trust you in your ability to cook well. I think you'll get your wish.

However, as the elderly are getting older, many of them still insist on working. This is not only to take care of you, but also to reflect their value. In other words, only through labor can they find their own sense of existence.