J.B.
I teach in a middle school...7th grade is tough!!!
I would contact the Guidance Counselor as the new school and see if they have a buddy program or a student-led welcome team. We use one in our school and it's awesome! There are a group of kids that will take the new students on a tour of the school and help them to get acclimated. This is done without adults...so the kids can visit and get real with each other. The welcome team then kind of watches out for the new kids...making sure they are finding their classes, sitting with them at lunch, introducing them around, etc.
I would also encourage you to go in to the school with him a day or two before it starts to see if you can meet some of the teachers. It might help him feel more comfortable in class.
Best of luck to your son and your family!!!