Guestfolio has the ability to trigger a Modification email upon update of specific data.
When selected, a field upon update will trigger an Modification email to be sent to the guest. The Modification email can be created exactly how you wish from the Automated emails page but perhaps the easiest way is to duplicate your current confirmation email and change the Type to Modification.
Modification Email example
Enable the trigger
From the Automated Email menu select > Email Settings
You are presented with a list of Update trigger fields.
Selecting one or more fields will highlight the selected triggers. You can select more than one field by pressing and holding ⌘(CMD) on a Mac or Control on a PC
Remember to click "Update automated email" when you have finished your updates.