Elephant outing, membership? (Phnom Penh)

I'm interested in joining that event and in the process of signing up, it appears that, being a basic member I would need to upgrade. The other thing that I noticed was that the first outing is free of some charge or another. Would that apply to any part of the cost of that particular outing?

I intend to upgrade one way or the other, but will go for a year subscription if there is a significant discount on that event.

Any idea when this trip may come to pass?

Thanks, John