Operating multiple low power devices from 1 adapter
Your common power supply will need two outputs - 9VDC and 12VDC. You cannot expect the devices that use a 9V supply to work if you inject 12V into them. They may give the appearance of working for a while but finally meet an early end.

Alternatively you could simply use two power supplies, one with a 9V output and one with a 12V output.