Airplay via Airport Express would be preferable in this instance, primarily due to the generally low quality of the Bluetooth implementation in iThings.
The AEX does require a network connection, preferably wired. It is possible to set up an AEX with a temporary connection, whch can be removed once setup is complete. If this is an issue their are inexpensive non network airplay-like devices from suppliers such as Neet.
Finally, there is the possibility of a wired option, but well specified docking stations, the best solution, are now quite rare. Depends on your iThing connections too.