I like the floor plan. I hope it will help you successfully pull this off. I'm looking forward to seeing this, it's one of my favourites in terms of style and structure. :)
these are looking good, i really like the design of water coming out the cave entrance.i can see 1 and 2 working well as a modelled version already, :)
In my opinion number 3 is still quite empty and there's something in it that would use a little more thinking. I would suggest developing either numbers 1 or 2 :)
I think 2 works the best, I can't wait to see your colourscheme. These layouts look very inviting and exciting
i think the hollow tree is a great idea (left hand corner of no.2) cool stuff George!