Orville and Wilbur flew together only

Orville and Wilbur flew together only once in their airplane for their father to see, but decided it unwise, because if they crashed, no one could carry on their work.

  1. Is there anything wrong with the above sentence?
  2. Who decided it unwise?

It’s not a great sentence. I would suggest this:
Orville and Wilbur flew together once in their airplane, so that their father could see them. However, they decided it was unwise to continue flying as a pair because if they crashed, no one could carry on their work.

Is that clearer?