Is this a formal or informal affair?

You might want to spread the word and request that people bring old funeral programs and photos etc all to look at. Bring your own to share too. Especially since you don't know many of the people. They are great starters, as well as providing great leads.

A printed out family tree (LARGE PRINT!) of what you know is a must to bring to share, and let people help you fill in the blanks