Well not having the mass and just having the ceremony makes it already feel more like a non-catholic ceremony. The church itself should not be scary they are usually very beautiful. My church is niether big nor very ornate but the church we are having it at (which is his) is very large and overwhelming. But even his church isn't scary... but hey I was born and raised Catholic, what do I know, it could be scary.
Maybe if you feel the church is large and scary try attaching the history of the church with the programs or better yet the invites on the back of the directions to the church. This will get them ready for the church and the more you know the less scary anything is.

Good luck but most people are not scared of the building they just hate the hour long wedding and you eliminated that.