You are proposing a building for public occupancy. You are clearly going to need permits and those permits will require an engineer's or architects stamp to be approved. If you don't have an engineer that is a member of your congregation, the cost of retaining one for such a simple plan is unbeliveably inexpensive relative to your project cost. One way that you might get a free-be out of it is to select a truss manufacturer for your roof, and ask if their engineer will render plans for your church.
In summary, nothing that you can obtain from this for'em will suffice as plans or engineering in obtaining permits for a public building. You need to budget $300 to $600 for simple plans.