Ideally this is what I'd like the source of the stream to look like:
That'll follow the downward flow creating the divider between the greens and the rock garden. Ideally you might want to make it look similar to this, unless that's too many prims.
For the rock garden section area I thought you might like to see some textures of rocks that I thought looked pretty good. This also gives you a bit of an idea of what I hope the sand will look like.
Finally for the garden section here's a few shots of some plants, general look and the cherryblossom tree I was thinking about. If we do manager this, it'd be great to have the animated cherryblossoms falling eternally like little snowflakes.
Now after the stream flows into the apartment complex, I figured it could flow out to the lower area where we'd have the small dance circle. I don't have any good shots of what I'd like for the dance circle, but I do have one of the waterfall and possibly if we can pull off the lighting effect one of the solitary tree near the stream I'd love to have:
Finally, going back to where the garden meets the steps up to the relaxation dais and where I'd love to see your style of airy tents set up I was thinking of having some steps with a few plants by it as shown in these examples:
Ideally I'd like to have the dais high enough we can support one or two houses (two stories) under it which I can rent out for visiters to that area of SL. The stream as mentioned before would flow down into one house and run along some kind of rock trench and out again to go to the dance area.
On the dais I'm thinking something similar to this work which you did a while ago
http://forums.secondlife.com/attachment.php?attachmentid=28444 but again, if the creative juices start flowing go with it and we'll see where it takes you.