The previous paragraph is in front of the main body of calligraphy, and the font is much smaller than the main body. Main contents of the preceding paragraph: The preceding paragraph specifies the name, source and recipient's name of the calligraphy content.
The next paragraph describes the date, place and author's name of creation. The position of the preceding paragraph should be higher to show respect, including name, title and courtesy name.
As far as your situation is concerned, there is no need to be too humble between grandchildren, just show goodwill and respect. So,
The previous paragraph can be written as follows: To my grandfather Shu Ya/Please give my grandfather advice.
The next paragraph can be written like this: Ding You, late autumn Sun xx, my poor handwriting.