Hi Roger,
The iPad audio output is higher level than that from PAW. I realised this when about to join the LAA 70th tour, having left my mixer/amplifier at home, in error. The EasyVFR Nav program which I use has its own system of audible alerts triggered by PAW so I connected the iPad audio directly to the radio aux input, adjusted the iPad volume and all was fine for the subsequent flights. The alerts volume matched the level from the radio OK.
Personally I would be uncomfortable just connecting audio from different sources together, without a resistive mixer network to compensate for differing voltages. Once correctly combined, no problem with passing the combined audio through a single amplifier, LM386 or similar.
Regards,
Chris