To email multiple registrants within a particular camp, go to:
Storefront (second icon down on the left-blue bar)
Click “Events”
Click the camp whose registrants you would like to email
From the registration page, make sure to select the maximum number of “Records per Page”
Select the square checkbox in the top-left corner of the registrants table to select all registrants
Click the three-lined box in the top-right corner above the registrants table
Select “Send Email”