Best practice to get several voltages from a wall adapter via buck/boost adapters
It's easier to step voltage down than to step it up.  So a good starting point would be an off-the-shelf 12V power supply.
Then to give the 3.2V supply, use an off-the-shelf DC/DC converter, or make up a simple linear voltage regulator.  Anything that runs off a coin cell only needs a tiny current, so there's no need to design a more complex buck regulator.