Feeds fot outside spa shower

Latest project, Deck with shower ,about 50 ft. from house.

At first I was going to use a small 20 gal elec heater protected from the weather under the deck. But now I,m thinking of tapping off the bathroom
hot cold pipes. Would use 2 watts backflow valves outside. could run 2 soft copper lines with jacket insulation inside pvc underground. Or use pex with the same detail. Never done this before . Will run by inspector first.
Any wisdom is appreciated Thank's Tool

I would think the PEX would be a good way to go.
It doesn't conduct cold like the copper does.

Thank's Terry