I consider it really sad to cancel a ski outing due to snow, unless it is genuinely dangerous out. The threshold for "dangerous out" in this context should be determined by adventurous people who are used to driving and otherwise spending time in bad winter weather, and who are equipped with the skills, clothing, tires, etc., to do so with confidence - i.e., many skiers, not your mother-in-law.
That said, I totally understand that when the weather is bad out not only do you have to expend the usual activation energy to overcome your OWN inertia, but also to plow past the discouraging words and body language coming at you from all directions in the form of people who think it's nuts to go out intentionally into a snow storm with the purpose of driving into the mountains.
It's kind of like fishing. If you want to catch fish, you have to go when the fish are biting. Time and tide wait for no man, and all that. If that time and tide happen to coincide with your family's dinnertime, something has to give. Deals must be brokered. You can't just go fishing by Doodle Poll - when it's least inconvenient for all the other people in your life. Well, you can, but you will miss out on the best experiences. Same thing with skiing.