Glad you like the tank. Good luck with yours.
Most of my wood is normal bogwood/mopani that I've just picked up over the years. The massive branch I was just at a large LFS and grabbed it out of a big bucket and it wasn't until I was on the way home that I saw an iguana on the back of the price ticket! I decided to risk it, but please note mate, that I have told you what I have done, not told you that it's OK to do it yourself- whatever you put in is ultimately your responsibility (although were it my tank and my responsibility I'd personally use the wood you've selected)!
It floated for weeks and weeks and probably months as it was very very dry, and where it was sticking out of the water lots of little flies started living. They didn't ever leave their little island though, I felt quite guilty when it sank eventually!
The rocks I got from a garden center, and they are slate rocks. £3 each they cost and there are 8 of them, all somewhere between house brick and breeze block size.
When you do the decor make sure the rocks or piles of rocks are based on the glass bottom of the tank, not on the sand. You do lose a lot of visible rocks which is a bit of a disappointment, but I've been amazed how much movement of the sand there has been in just under a week- a rock stack directly on the sand would have collapsed for sure and possibly put 20 kilos of rocks into the glass. Must remember to thank CFC for that little nugget, read many moons ago!