how much are you willing to spend?
I would receommend something in the line of a Torano natural cigar like the siganture selection robusto. I know I'm probably going to get killed for this but maybe a box of Macanudo's would serve as well. They are good quality and won't offend. Most here don't like them, but if your father smokes phillies then I doubt he'll know the difference.
If you're looking for something cheaper you might try the Don Tomas or Astral line. Both lines are exceptionally mild (the Astral in particular is way too mild) but they're inexpensive and o.k. for a beginner.