This is a workaround I use, the order of actions is important:
- Export the participants' list for the session (to excel for instance)
- Use add/remove participants for the session to remove all participants (this send the cancellation emails for the previous session dates)
- Change the session dates to the new ones
- Use add/remove participants to add participants 1 by 1 - this sends the new updated invitations to them. I use the exported list form step 1 to search the participants that were already signed up.