Guys and gals, so I appreciate all the advice and thoughts on this topic so far. I'm definitely going to contact Dan. I realize getting more expertise on this topic is what we (my church) needs to make a good decision.
One thing I did do in the last week was touch base with a geo designer - not installer.
He came in and brought up two very important ideas.
1. Why not consider using ice storage?
2. In the winter, have a back up boiler.
His point matched a few of your comments. Using a hybrid system, we can capitalize on the low operating cost of geo M-F (and Saturday) by just running (lets say for the sake of argument) a 20 ton cooling system. The system would also be building up ice in a ice storage tank. Then on Sat night or early Sun morning, the system kicks in higher gear and starts using the ice storage as a quick heat sink for the peak usage on Sunday morning. We don't have evening church services. So other than weddings, we are virtually needing a AC system for just 5 hours on Sunday morning.
Likewise, he said, you could run the equivalent of a 20 ton geo system in the winter, then on Sat night (or early Sun morning) the system kicks the boiler on to preheat the water going into the geothermal heat pumps. Again, the point would be to keep the church at 55 degrees Mon thru Sat, then get it up to 68 - 70 degrees for just 5 hours on Sunday. (or the occasional Sat wedding).
I really, really like the idea of a hybrid system. Instead of installing a 40-50 ton geothermal system, we have the best of both worlds.
AND mind you ,this idea came to me from a Geothermal guy! You'd expect him to say, "go all Geothermal!" but he said upfront, this is about how to get the best bang for you buck.
Therefore, if we can cut our 40 ton quote ($350 to $400K) in half, for just $200K, then it's a much better selling point. ASSUMING this design is even possible. This was just an idea at this point.
One comment was why not keep existing steam system, but I am afraid the pipes are too old. We have an average of one leak per heating season - usually one small pin hole leak that opens up and blows steam out. And of course Murphey's law kicks in - it happens on a Sat night. As a result, I have to open up the walls and repair the pipe, repair the wall, carpet, etc. The boiler is newish, but the pipes and radiators are original, or damn near original! (The building was built in 1931. )
See pics attached for an idea of the monster we're talking about. As I said, 53 ft ceilings. LOTS of space to cool and heat.