As far as your other difficulties, we had a meet go on as scheduled even when the host couldn't make it due to his own serious medical problems. People who wanted to attend on the original date did so, with alternate hosting arrangements (I didn't attend, so I don't remember what the plan B was). When the host was once more up to hosting, he set a second meet date.
That's probably a reference to my New River Gorge meet a couple of years ago. I actually didn't do another meet there; but I had published the itinerary far enough in advance that everyone who was coming knew the routing and could plan accordingly. Plus, I knew a few days in advance that I wasn't going to be able to make it. I have, however, attended meets where the host bailed the day of the meet, and attendees and a last-minute-substitute host had to scramble to make things go somewhat as planned.
As far as weather goes, Froggie hosted a meet in Slidell, La., with a hurricane headed for the Gulf coast. Since the landfall wasn't going to be for a couple of days after the meet, it went on as scheduled. I remember he floated the idea of canceling, but I was already en route when he did so and said I didn't mind coming on down since I already had the trip planned.
Cody's Chattanooga meet was indeed on a rainy day. One of the Columbus meets about 15 or so years ago was marked by really strong thunderstorms.
I'm not sure I understand why the "my relatives split up in Houston on their return trip" factor would play a role in canceling the meet.