I'd have them pre- wire to some flower beds that you have in the pool design, around the pool. Bring the wires back to the place where you would like your receiver to go. It doesn't have to be in an outside cabinet, etc. Get a receiver with Airplay and App control and it can be controlled with your phone/ipad, etc remotely. I have mine mounted in the attic above my outdoor grilling area, for instance. I prefer to go with wired whenever I can - more power, fuller sound, etc. However, some of the wireless options are awesome these days, so that is something to consider too. If you go with Sonos or similar, I think you have to have power for every speaker location so that is another consideration. With a typical receiver/speaker connection power is not required for each speaker location, only the speaker wire is required.
I'd also have them run some low voltage 12 volt wiring for landscape lights, etc. I retrofitted mine after the fact and it was a pain. Have them run conduit with string in it to any locations you may want to use in the future that you may not think of now. That way you can pull your own speaker/landscape lighting/power in the future and not have to dig up concrete decking, etc.
Have fun!