I've thought of planing my deck wood also. As said, it would be a real PITA, but it is doable. I think a floor model planer such as a Powermatic would be the best to use. A bench/portable would do it, but expect to do a knife change when done. Especially if there is any dirt in the wood.
A pressure washer works, but not if you use high pressure. That digs out soft wood and leaves a mess.
We used 1 cup vinegar, 1 cup Arm and Hammer washing soda, and a gallon of water to scrub the deck with a brush. Wow, did that do a good job.