"I'm feeling skittish about DFW..."

Why? If you know the reason for cancellations in the past you also realize cancellations are possible no matter which airport you choose to fly out of (Your odds of cancellations are far greater in PHL than in DFW for late December, IMHO). I agree with others that you are overthinking this. Some of my best travel memories are those trips that didn't go as planned and that includes flight delays and cancellations.