Python or PyPy for small group and large project?
Python (assuming you mean the CPython implementation) and PyPy are not frameworks, but implementations of the Python language. Note that they implement the same language. I'd start with CPython because it's industrial-strength today, and the multitude of Python libraries, frameworks and extensions all target it. 
PyPy looks promising, and it may become a serious contender for the most popular Python implementation some day. But that day is still far away, and if it does arrive it won't be without PyPy's ability to run CPython libraries without modifications, so I think you're safe for quite some time.
Early stage of planning a large project - difficult decision of choosing frameworks :)
In mind:

"select way - run fast".
 Select technologies with growth opportunity, prototype as fast as possible.
"look at horizon - build a ship".
 Understand the scope, invest in difficult decision but reach the goal.
"take the best - enjoy the ride".
 Bring the best team, do not let them fall aboard.

Choose from:
HTML 5, CSS 3 - PyPy 1.4/CPython 3 + Pylons/Tornado/Django - CouchDB/MongoDB/Riak + Erlang?
First step: 3-4 developers in team + 1 admins + 1 designer.
Designer - View + Service Developers - Admin - Balance + Structure Developers
Second step: 5-7 developers in team + 2-3 admins + 1-2 designer.
Updated: Python + Pyramid (Pylons) + Couchbase (CouchDB)