The day before the trip, Mom helps August pack. She folds all his clothes and puts them in the duffel bag and suggests he take a book in case he can't sleep. August decides to take Baboo, a favorite stuffed animal, in case he needs help sleeping. Mom tucks him deep into the duffel bag, zips it up, and notices that August took down his Empire Strikes Back poster. August explains he's trying to change his image, and Mom seems to understand.
Mom's level of involvement in the packing process and the items that August mentions perfectly encapsulate his in-between state: he still requires assistance and a stuffed animal, but he's attempting to seem more mature by eliminating some of the childish items in his bedroom.
Mom reminds August to wear sunscreen and bug spray and tells him not to get his hearing aids wet. She then comments on how much August has grown up in the last few months. She kisses him on the forehead and decides it's time for him to go to bed. Though she tries to lie down with August, he insists that he can put himself to bed. He promises to write her letters and then reads until he falls asleep.
When Mom makes no protest to August putting himself to bed, it shows that she recognizes that August is starting to pull away from her and needs this space to figure out what kind of person he wants to be. When August asks for this independence, it tells Mom that she did a good job giving him the confidence to want it.