I really like your basic idea to share information to all family members via a site. However I think some features would be good to have:
Almost all Genealogy software use a common format to exchange information (import/export). This format is called "GED".
In order to avoid double entry of information from already exisiting sources I would recommend that you provide support to IMPORT information via GED format files. The pace of expansion will be boosted quite dramatically.
In order to find information about some distant relatives and to import them into your own research I also would recommend the EXPORT function to be implemented.
