Blog Vs Wiki

I am interested in setting up an information sharing facility for the North East Libraries - Focus on Children. The idea was mooted at our meeting in Dorrigo last year, and with Mylee's encouragement, and support of the group it seemed like a worthwhile thing to do. I was all set to create a Blog ~ until I learnt about Wikis, and now I'm not sure what would best suit our needs. What do you think?