There are a couple different ways to make it easier to email a larger group without forgetting anyone: contact labels and Google Groups.
You can create custom groupings in Google Contacts by attaching the same custom label to all of the people in the group. Once you create the label and add the label to all of the people, you can use the label in Gmail, Calendar, and Drive. Labels are best for smaller teams (2-14 people) or for your own custom groupings, such as an easy way to invite the handful of people working on a specific project or an quick way to email all the people supporting a specific student. Learn more about labels in Contacts.
Good to know: Contact labels can't be shared, so each person must create their own labels and attach them to all the people. This, however, allows for customized labels and groupings.
Google Groups are like a listserv, meaning that each member of the group receives a copy of each email sent to the group's email address (firstname.lastname@example.org). Groups are best for larger teams (15+ people) where it would be helpful for others to also be able to quickly & easily email the entire group, such as a school site or department who wants an easy way for everyone to be able to email the entire group. Learn more about Google Groups.
Good to know: Only DoT can create new groups, but the admin/manager of any team can request a Google Group. Once DoT creates the group, it's the admin or team manager's job to add and remove people from the group as needed. DoT will not make groups for emailing families or students; schools and programs should use SchoolMessenger.