SwimOffice lets you restrict meet declaration to Billing Groups or Squads/Roster Groups and Locations, along with only emailing those groups you select.
Click Events & Competition > Team Events in the side menu.
Add a new event by clicking + New Calendar Item > Team Events, or click the desired event name and then click the Edit button at the top of the open window.
Fill in the desired info if it's a new event.
Scroll down to the EMAIL NOTIFICATIONS section.
Check the Also, Restrict Declaration to ONLY the groups defined below box.
Select the 2nd or 3rd radio button to restrict entries to certain Billing or Squads/Roster Groups and Locations, respectively.
Click in the fields to select your desired groups. You can start typing to narrow down the list.
All other groups will be excluded from entering this event.
When finished, click Create or Save.