4th weekend begins on the 25th. Mom has Thanksgiving break which, according to that, ends on the 25th. So, as long as Mom returns the children at 11.59pm on the 25th, she's good to go.
Of course, I expect parents to iron out the small details in the favour of the children ... not each other. Then again, reasonable parents are hard to find in this day and age, don't you think?

