To email the parents of children in a group(s), go to Communicate > Email >Send. The email is using the Churchteams Report feature; therefore, you can filter to select the group that you want to email, then filter to the parents of the kids in that group.
Once on the Email page, in the middle Filter column, click: Groups/Registrations > Group Involvement > People currently in a group (see image below). Then, individually pick the group you want from the Groups dropdown menu (1) or by Ministry from the Ministry dropdown menu (2).
This action alone would email the children in the group. Instead, to email the parents of the children in the group, after you have selected the appropriate Group filters as mentioned above, click the filter heading People > Family/Household Attributes > Select Related Family Members, and choose Adults (3). This will email the adults in the household of these children, so long as they have an email address on record. Finally, the email the kids/youth as well, make sure that you check "Include selected family member" (*) at the bottom.
Run the report by clicking "Go!", then choose "Email via Churchteams" to open the Email Editor.