The girls go to Spain all the time! Joel's dad/family own a holiday home there and have done for years, so I assume its just a normal thing for them. Joel's nephew was in their last video at the amusement park and I think he lives in Spain usually so they've probably gone back with his sister for a few weeks.
Tbh, Sarah was in the right in the stationary video and was the only one speaking some sense into the girls. Why would you pick up only one ruler instead of the whole kit where you get a ruler, pencil etc for the same price. More for your money and even if you dont need it then, you will need it down the line. Just makes logical sense. I think Joel is the one who encourages the kids to get whatever they want and Sarah is the rational one who steps in.