As the family is getting ready to leave on the camping trip, Richard mentions that the dog has been missing for a week. But toward the end of the movie, Richard says the dog bit him several weeks ago and he had him put down.
When the family first arrives at the campground, as they are parking the SUV, you can see Pennsylvania license plates on the front of the SUV. Pennsylvania vehicles only have license plates on the back, they do not have tags on the front.