Well, if it was me instead of Ben, I'd:
(1) Look up all available documentation regarding Beltane's claim.
(2) Find the nearest thing available to a Native American shaman, and ask his opinion.
(3) Do whatever seems most entertaining, given the information I've collected.
I had very similar thoughts, but I'd require Beltane
to produce notarized
(i.e. independently authenticated) documentation of her claim. I'd also make sure to find out what tribe makes claim of the land (and contact them on the matter). While she's off collecting that, I'd sit down with Lily and the other interests in the arcade and discuss what to do.
I'd also like to mention a little legal precident called "abandonment". A church that's been left unattended / unclaimed for long enough needs re-sanctifying, so I'd expect that an "ancient hallowed Indian ground" that is now in a developed area - complete with a decades
old house - would either have outstanding claims against it or no longer be remotely "hallowed".
But as to what specifically to do...
The arcade - or some part of the grounds - could be rented out for a function. But there should be conditions on this, such as "no nudity", "no open flames", etc. Perfectly reasonable requirements, but I doubt Beltane's coven would want to agree to them. Renting the space and time would be a business arrangement.
Which has absolutely no bearing on the religious issues. Religion isn't the arcade's business. Allowing Beltane's coven to celebrate there also opens the door for the "church ladies". So no matter what authentic proof Beltane can produce, Ben is more than justified in refusing her.