We have about 2 TB of data distributed across literally thousand of tables in PostgreSQL 9.4.9, and we think that we should be moving the historic data to a more report-oriented and efficient solution. Which is the proper solution is what troubles me, as I'd like it to be AWS based (perhaps RedShift, EMR or other) as our platform resides there, but even within that ecosystem, there are several approaches to be used. I'm aware that asking about the choice of a specific engine and/or solution is offtopic, but I'd certainly like a suggestion of what kind of tools to choose from, without necessarily implying the use of single one. As a team, we have no knowledge yet of the data warehouse architecture and, just a bit of the big data technologies, but we certainly have to study on those subjects.
I think you should be thinking about what your end state is going to be.
I.e: "What is the requirement"?
The requirements should be driving the solution. Not the other way around.
What does the business want?
What reports do you need? What outputs?
Will your reporting solution benefit from aggregation? Would an OLAP cube be of benefit? Will you be transforming or denormalising the data?
Will your DW be fed from one system or many? If many: will it be application agnostic?
What display tools and technologies are expected? Any compatibility issues that might limit platform selection?
How long do your current reports take? And how fast do they need to be?. How fast is fast enough? What changed?
Can you produce the reports you need now with the data you have?
Are conventional reports still acceptable? Or does the business now need/want dynamic interactive tools? Reports? Dashboard? Exploration tools? Mobile?
How recent must the data be? Is yesterdays data processed overnight acceptable? Or do they need near real time?
Do they want analytical or operational data? What happened over the last 12 months or what happened this morning?
Once you have a clear requirement, it will allow you to shortlist viable solutions. Within your shortlist you can start to express preferences and pros and cons for the evaluation process.