- don't forget in the education process to make sure they know that the 'non-holding' side is also 'protected' out to a certain distance to enable joins?
Exactly - and to allow for errors in flying the hold.
Holds don't only separate you vertically from other traffic. In busy airspace traffic at the same level has to be considered too.
Irrespective of the type of join, once over the Fix and Heading Outbound the aircraft will be in the Protected Area of the Hold (indeed the Teardrop and Parallel Joins mean the aircraft will be within the 'standard' Racetrack Pattern).
ATC would like to know that you have remembered that you are to Hold (stay within a certain area) and are not going to fly on miles and miles outbound from the Fix.
Therefore 'Entering the Hold' should be reported the first time over the Fix.