Dennis @ PerfectForms
You could create a behavior on when the checkbox group changes field data. Use a Multiline Text hidden helper field. Start by setting the helper field to empty. Then create a Multiple Branch or a series of simple branch objects to populate the hidden helper with the values of all the checked checkboxes separated by commas (no spaces). Then create a role and make the owner of the role the email addresses in that hidden helper field. Send the notification to that role.