Thanks AVR-fred!
I was also worry of the isolation between the two secondary coils since they are usually wound on top of each other.
Do you know of any specific transformers for option 1, PCB mounted?
I also thought of option 2 as well. 24V DC is locally available but I couldn't find any small sized PCB mounted DC-DC converters with enough isolation that would do. And since there have to be two of them, size is an issue. The PCB measures only about 80x100mm