My suggestion is to have a table of Park Managers. In fact you may already have that to drive a drop-down list.
Then create a specific form which will end up getting emailed to that Park Manager which has the embedded report of whatever you want.
Put a field on that report which is just a date time data entry field and create an "OPEN" notification the park manager.
Tested by manually entering any Date / Time to that field. (tip, you can just type "n" for now and it will auto complete.).
Once you have that working then create an admin table where there is only one record and use that one record being edited (say a date / time field being set the the current date time with a Formula URL button) to trigger a Pipeline to update all of the park mangers' records which have up coming reservations with the current date time into a trigger field for the Notifications. When a pipeline runs to update multiple records like that these are seen as individual record changes which will trigger the individual email notification that we want.
Mark, thanks for the great response. Will get to work on that and update you once it is working.
