iPhone is voice for hands free however iPad is just music which is Bluetooth 2.0 A2DP
That allow music to be sent from any blue tooth device. What you need is a Bluetooth 2.0 A2DP sound system. see parrot.com for ideas plus many more on searching the net.
Phone Hands free systems do not support music unless the system sports A2DP I use. Parrot 9200 A2dp sound system for both hands free and music
Hope that helps