Codes are the result of failed tests that occur at regular intervals. Most likely what ever component is starting to fail no longer meets the specifications that the test looks for. Note, "starting" to fail. It may drive just fine for now, but that's why it throws a code, as a warning. It's on it's way out. I suspect that if you continue to drive it you'll find out how soon the transmission will actually die.
You've towed a hybrid trailer with it for 92k miles. That trailer is already at or over your max towing capacity and most likely the frontal area drag of the trailer is what contributed to the transmission. Not to mention you've got 4 kids, I'm sure you're way over your cargo capacity on the van. It was really only a matter of time...