The first thing that most family members are interested in is just that: family. Who are we? Where do we come from? (Though there are many other vital and interesting questions and issues that we hope to cover in the near future.)
These are good questions that require good tools. For that the head of family genealogy joined the Internet revolution using GeneWeb and more recently has started to also use GRAMPS. Both of these are free software and can easily handle the many thousands of family members.
As long as your family tree software can import GEDCOM (version 5) then it should be compatible with the central family database.