I would suggest you use a Sonos system. Each zone would use a Sonos Connect or ConnectAmp depending on the number of speakers per zone and how loud you want that zone to play. The ConnectAmp is 55 watts x 2 and can drive 4 speakers. The Connect can be used with any amplifier.
It will give you access to internet radio and every online music service. Also plays files on computers and phones. Controlled with any Android, iOS tablet or computer with free apps. These are just used as remotes so they don't have to be on while the music is playing. Very reliable very easy to use. For private parties you could let your clients bring their music.