Hello and welcome back to planDisney, Doreen!
You have asked a great question, and it is one that I have personal experience with. When my son was younger, I remember he wanted to go on a specific attraction, but his dad and I sent his older sister to ride with him. Unfortunately, she could not accompany him at the time because she was not of age, so my husband had to take him. Having said that, as long as the person accompanying your 13-year-old is 14 or older (which, in this case, they are), they can enter the theme parks without the parent. I understand how that can come in handy, especially now that my kiddos are older.
Before you let them go, ensure they have a theme park reservation and theme park tickets, as well as any additional funds they will need to grab a bite to eat or pick up a souvenir they have been eyeing. I know they will have the best time.
Come back if you have additional questions.
Have the most magical time at
Walt Disney World Resort!
Raquel