Lord of the Ring / Loth Lorien giant tree scene process

Hello everyone!!

I need help of the better community in the CG world, you guys.

I were reading lord of the rings and i thought would be great to recreate that giant Lothlorien tree where Galadriel lives.

The problem comes when i realize that rendering the scene that i have in mind would be very heavy.

So I tell you things I want to introduce in to the scene,

I want to do a river passing down the roots . (Fluid System)
I want to do vegetation on the ground, flowers, weed, bushes, trees, etc, its a elvish forest so.
I want to do more elvish arquitecture for all along the tree, including elvish lamps, maybe some fire (fire simulation), some flags (cloth simulation)
And also i need to place some human character so you can see proportions, the tree its giant.

anyone knows how to render all this in a single scene?? I know that i have do few diferent render and then mix it togheter. But i dont have a good computer,
and i also want to make little animation for kind of presentation…I think it’s possible, what do you think guys??

Now i share some quick renders so you can see what i have done until now…

//(I know that the HDRI dont matches well, only there for…trying)
// (I also know that materials still dont matches well, i can fix it later)

I need your advice, my friends. Whatever you think about it pls tell me, i need feedback and all your little thinkings.Project its OPEN so i can do
whatever changes that you imagine, no problem for that, but keep the idea, Giant Elvish Tree (Lord of the Ring style)

I think it can be a beautyfull scene. (Imagine that beautifull animation fliying inside the architecture, or even fix it for a videogame)

Sorry for my poor english.

Pls help me with your ideas, i will be thanksfull.

The problem comes when I realize that rendering the scene that I have in my head would be very heavy.

Here it is new stuff.