Oh, so your community was small enough that you ended up being able to edit the titles of each member individually? That sounds fine.
A search turned up another, automatic solution, which is to use the badge system to automatically set the member’s title based on their trust level.
Jay is right that you don’t want to tinker with the naming of trust level groups themselves because they have a particular purpose in Discourse. You don’t need to worry about that too much as you start your community, but if you are interested you can read up on it at Understanding Discourse Trust Levels .