What great questions!
I really enjoyed seeing family. You and he will have to negotiate with the kids; he'll want/need to leave and ride, they'll want to see Daddy. If he's going west on the TransAm, plan for a couple of days around southwest Virginia or eastern Kentucky, if at all possible. He'll need to relax and recharge in the mid-Appalachians.
The Most Important Thing, after what you've listed, is the Adventure Cycling map series. Second is Bag Balm, followed closely by Chamois Butter. IMHO, of course. I assume he'll have rain gear, sunscreen, sunglasses, cell phone, ATM card, etc. For your piece of mind, if you're like my family, frequent (daily preferred) "all's well" messages via cell phone or email will likely be appreciated. And be patient -- just because it's dark on the east coast doesn't mean there's not two more hours of daylight for him to ride out west.
The Garmin 705 looked/looks intriguing for its combination of yellow pages and location. There's no other need for a GPS I can think of. I'd suggest you try to be available for emergency motel look-ups, especially in the west. When he needs a warm, dry place with a shower, and has 15-20 miles to go, google "motels town state." Then call for room availability and price, make him a reservation, and text him back. (He just lost cell coverage right after he called you!)
The Most Important Skill to develop is to figure out where to send packages. If you can afford overnight or 2-day delivery, that may not be such a big deal. Guessing how long it'll take a package to arrive, how far he can travel in that time, and meshing that with post office hours is an art form. Also, try to mail packages the very next day. It's easy to wait a day or two, but then your package will miss the cyclist.
I was glad I took a netbook and camera. Crazyguyonabike journal sometimes met the "all's well" requirement, and I felt like I was sharing the trip with parents and siblings. (My wife demanded frequent telephone calls.)