Sounds like you are doing your homework ahead of time!
You have a nice setup in your yard. Likely the bees will pollinate your trees and garden, but most of what they collect will not be from your yard. But rest assured that there are plenty of pollen/nectar sources around.
Hive materials - I'm not familiar with the decking material, but I'd recommend just going with pine or spruce. It is cheap, and may not last as long, but at least you know what it is made of. And as long as the paint/stain stays on the outside of the hive then there isn't any issue with airing it out, etc.
Water Source - The bees will likely go to the source that is 50' away, but it is good to keep one closer as well.
Neighbors - it isn't usually the next door neighbors that are the problem, it is the one paranoid 3 houses down that will flip out on you when they find out you have bees and they, their kids, and their dog has deadly allergies to any kind of insect bite, sting, touch, etc.
Sometimes it is better to ask for forgiveness, because if the neighbors don't know anything about bees then they may be afraid, but if you have them for a while before the neighbors find out, then they can see that they aren't a problem. But it is good to talk to them first if you know them and they aren't afraid of their shadow. It's good to have a backup plan as well.
Bee clubs - Yup, highly recommended to get local contacts. The internet forums are great, but its sure hard to diagnose something from 500 miles away (or however far).
Read lots, and have fun planning!