I am so LUCKY!
That this happened while I was in our driveway, idling forward into my parking spot, and not on the road where I just drove home from school 55 mph with our son!
The plan was that we would replace my van in April, after mud season.
I guess the plan is changed.
My husband's birthday is tomorrow, and he was taking the day off anyway.
Happy birthday, my dear: we're alive!
Edited to add: I'm not 100% sure what happened since it just happened and is still sitting in the slush in the driveway, but my first thought is broken axle or broken tie rod end. Here's a close-up, in case you know all about "wheel fall off".