You can open their files, but not vice versa. And do you mean Indesign 2, or CS2. CS2 can open .inx exported from CS3, which can open .inx from CS4, which can open .idml from CS5 (I'm guessing you meant CS5, not ID 5, which is version CS3), but you must have all the versions, and the file may not be recognizable. There is no way to make any sort of file from a later version that can be opened in InDesign version 2.
Well, the church has the Bridge (which I have no idea how to use), but they didn't have Illustrator or Photoshop. They have some other Adobe apps, so I'm thinking they bought all of them separately.
I on the other hand have CS5.
Well, I didn't think it was going to work, and it sounds like it won't. Not surprised by the answer, but at least it saves us trying to go backwards three versions.