Right you are, Carol. My hybrid also falls into the pop up category for this rule.
So genhand, your mom can bring her pooch and keep it with her at night, which is what the Wonder Beagle does, but poochie can't be left unattended in the pop up - so we kennel the Wonder Beagle during the day, and bring him back to the Kiwi when we are done wandering and in for the night. Their reasoning is sound - not just for noise control, as 2goofycampers mentioned, but also to prevent escape for a lonely pooch looking for his family. Be sure to mention there will be a dog when reservations are made and that you must be in a pet loop so you are assigned appropriately, and be ready to pay the extra 5 bucks a day for your pet.
Also be sure to bring proof of vaccination for your pet, which you will not only need for the kennel and FW requirements, but also crossing the border since you are from our cold neighbor to the north.