From 10-20 feet away, how can we command an ipad to play music to a hardwired external speakers: Synchronized swim group doesn't want to get out of the water to start and change music?

Our synchronized swim group owns an Ipad that we directly connect to a system that sends music to both a large external speaker & an underwater speaker. While in the pool, we want to use voice commands to have the ipad play our music. Note that we are in Florida, so the ipad is on a cart several feet away from the pool to keep it out of direct sunlight. The majority of our music is downloaded on the Ipad from Apple Music. We do have some MP3's in a seperate folder. We have wifi at the pool. In the past, songs that weren't downloaded experienced some playback issues probably from weak or interrupted wifi signals.

What would be the best way to use voice commands to play the music? (Siri, an external smart speaker set on the side of the pool or something else?) Set up instructions for the prefered method would be very helpful. We are not very tech savvy. Thanks