How do I make a group to cover several people's emails?

Create Smart Groups in Contacts on Mac

A Smart Group is updated automatically based on criteria you specify. For example, you could create a Smart Group called “Book Club” that includes any contact who has “book” in the Note field of their card. Whenever you use “book” in a contact’s Note field, that contact is added to the Smart Group.

Note: Smart Groups can include contacts from any account.

Create a Smart Group

1. In the Contacts app  on your Mac, choose File > New Smart Group.
2. Enter a name.
3. Use the pop-up menus and text fields to set conditions.
4. To set additional conditions, click the Add button . You may need to scroll to see more condition rows.
5. If you include a group in a condition (by choosing “Card is member of” or “Card is not member of”), you can’t delete that group until you change the condition or delete the Smart Group.
6. Click OK.

https://support.apple.com/guide/contacts/create-smart-groups-adrbk1005/mac

Did you get it working?