Great plan you have ... and it'll be even great if you can come up with some that are unique to your family.
What are some of the family sayings that your GS would know?
Ones you are proud of ... and perhaps ones he "hates" to hear, though in years to come as an adult, they will remind him of us family members, and what they'd say.
Any remembered words or phrases he said once, though the family have continued to repeat for years? when he was first learning to speak? later on?