Including friend in family vacation​

My 15 - year - old son wants his best friend, also 15, to join our 8 - day summer vacation full of outdoor activities. His friend's single mom is poor, and the boy has never really vacationed. I'm torn. It would be great for the boy, and my son, an only child, would have a companion. But we're not rich, and it'll cost more. Also, I'm not close to the mom, and I'm nervous about taking care of another kid far away. Plus, I hoped for a normal family getaway. What should I do? #FamilyVacation #IncludingFriend #TeenageSon #SingleMom #CostConcerns