Map cluster interactions

Hi all!
I am in the process of designing a piece of software that heavily revolves around a geo-spatial view (interactive map). I would just like to point out that I have never designed anything like this before so I’m completely new to this area which is both exciting and terrifying at the same time. Most if not all of the interactions used have been heavily inspired by other apps out there; people are used to google maps, so what does google do? However, google do not have to manage clustering - please see fig below.

By design the out of the box interactions are; double click to zoom, which makes sense to me because this is the standard axiom of any map if you’re not using the mouse to scroll in and out. So in my design it is a single click to view details and a double click to zoom / start splitting the clusters. However, a more senior member of the project team is adamant that we will have to retrain our users if we introduce this because and I quote says “everyone expects a single click these days” :S. Now I am more than happy to test this theory with users however, I was just wondering whether anyone else has worked with maps and has any experience in what the interaction in this case should be?
Thank you in advance

I have read quite a few things by the Neilson Norman Group but most comments are directed at website based design, I’ve been finding it really difficult to find documented design patterns for GIS systems.
I don’t agree with the senior member either but I’m easily convinced I’m wrong because of how out of depth I feel, and I have no other UX/UI team member to converse with so I really do appreciate your view. I honestly do not know where he has gotten his opinion from and I will ask him to elaborate on it further.
Thank you!