Then give them the budget number with a clear scope of what they will get for that budget:
1) Plans
2) X number of receptacles.
3) Fixture allowance.
4) Fire Alarm (if required).
5) XXX size service.
Do not give them a set of plans back, do not spend too much time developing plans, just do enough get budget number.
Whenever you meet with them but especially when you go back with your thumbnail quote... carry a full roll of plans and a stack of spec papers with you. Set them down (heavily) on the table. Point and refer to them as an example of what they have NOT paid to have prepared yet (structural/mechanical/etc).
The church committee may have no hint of a clue (let alone an actual clue) of what is entailed in building plans.