That’s a pretty long room. Two Fives and a One wouldn’t be too much. I wouldn’t set the Fives up as a stereo pair though because of the speaker distance.

Or consider using four Ones, one for each corner. Or two Fives on the pool side of the room and two Ones on the other side.

I would also consider using a wall mounted Echo Dot for voice control rather than relying on the Sonos One microphone. Echo devices are much more reliable when using Alexa than Sonos speakers especially if the One is going to be mounted near the ceiling.

ONE’s will deal with the humid environment better than FIVE’s, but have less bass than FIVE. That room is also very ‘live’. I would vote for any excuse to add more speakers.

How do you spend your time in that room? If there is significant time spent in the waiting area, arrange FIVE’s for the best stereo image in that area and use ONE’s to fill around the pool area. More speakers will allow you to run at a lower level and still have coverage. With this strategy you’ll have less trouble with reverberation.

MOVE will also deal with the humid environment and offer more bass than ONE.