We've written about terrariums a few times before (here and here) and love them for the self-contained little worlds you can create. The terrarium vessels we see in stores and catalogs are beautiful, but expensive so we've yet to take the plunge. But using baby food jars as terrariums takes that excuse away and is a good way to reuse something you probably have dozens of.
Susan Beal has written up a tutorial and supply list for making these which you can find at CraftStylish.
Each family member could choose a figurine to include in their own terrarium or why not use this as an activity at a birthday party so everyone has something green to take home?