Jay, I held back when you posted this, because it seemed like what you were asking for was way more than what I would recommend. But on second thought, your situation sounds a lot like mine. The distance, the head, the trees. What I would do (if you can get electric down to the water) is put a 2" Tsurumi Trash Pump in the water source, poly hoses up to a poly tank above the trees, then gravity water from there. Easy winter storage and no gas engine upkeep. I've used those pumps for years in construction dewatering, and they are remarkably dependable.
just another thought.