Book selling advice, please re Google Shopping.

[RameRetro]

I wonder if one of the seasoned book sellers may be able to offer some advice?
I have a collection of vintage books from a series of volumes that I wanted to sell as one lot. Normally, when I sell books individually, I would include the ISBN number and they successfully get uploaded to Google Shopping.
As I am selling more than one, I wonder if can or should include all the ISBN numbers, or if I leave it out and just put "EXEMPT" in the barcode box, which I would do for vintage items other than books.
These are collectable and popular titles and I would be competing with sellers on TOS, so I would like to get this right, without flouting any Google Shopping or Ebid rules.
Many thanks
Chris

Quick postscript: I can't find any ISBN numbers, They are children's books, getting on for 50 years old.

[RameRetro]

On further examination of the books, I can't find any ISBN numbers in them. They are children's books around 50 years old. I guess in the absence of an ISBN number, they can safely be listed as "exempt"?