personally i like to write the mvc skeleton myself and decide which frameworks will be used and go from there. or a leader for the backend who assigns out small tasks as small as a "function to draw this btn or move this element" or to "find me a library that does X and is..." and then he can merge them in... then once it takes shape you can share the files and the work.

i suppose usually for me one guy (say techsupp or network admin) sets up the svn/webserver/db, one guy decides on frameworks, one guy writes the skeleton, one guy starts on the interface, art guy does art stuff, typically the lead dev is watching over all this and merging stuff and when ready gives orders and access to the repo. if theres at least some structure and one template or working file/interface the juniors will have more success imo.