1

I don't know what "won't cost us a fortune" is in $$$ to you.

If you intend to invite and/or pay for 30-50 attendees from Oz, as you indicated in another thread, you have probably reached my definition of a fortune.

2

Eh, a church, synogogue, temple, city hall?

3

You need to be wayyyy more specific.
One very reasonable spot is the Sheraton on the big island.
They have a lovely gazebo overlooking the sea, and unlike Maui, or Kuaui or even Oahu, you can still get in there for about $129/night.
Downside, no beach, its lava rock.
So you get to see manta rays from your room each night, but all your swimming will be in the pool.
Last time we stayed there two weddings took place and it did look lovely.
They have a small white chapel right on site.
Off the top of my head that's the lowest price option I can think of, but keep in mind your guests will have to take an inter-island flight from Oahu to Kona.

If you are budget minded why not just stick to the Whitsunday's or Ubud if you plan on having 50 guests from OZ?

Edited by: homerjhomerj