That's a lot of ground to cover in three days. Be advised that parking permits must be obtained in advance at Old Rag due to its popularity. If it is lunchtime when you visit Monticello you might enjoy lunch at Michie Tavern. Many excellent restaurants in Charlottesville. C&O is always excellent. If your son wants just a good hamburger and fries then Riverside Lunch(either location) is unbeatable. Bodo's offers the beast bagels south of Times Square. Wilderness Battelfields lie between Charlottesville and Fredericksburg.

The food at Vivace was very good - excellent eggplant parmesan.

After Mont. and UVA, my third pick would be driving a section or 2 of Skyline Drive. They have great and challenging hiking and 2 lodge areas and restaurants that would make a perfect 1 nite stay. An easy drive from UVA.

Also look at Wintergreen Resort between Charlottesville and the Skyline Drive. It is a great place to stay with a lot of activities that would interest a teenager. We took a very challenging and fun hike the last time we were there.
www.wintergreenresort.com

If your son enjoys hx, you might want to consider Mount Vernon while you're in northern VA. Lots of ground to cover as someone said in 3 days mixed w/ business & wide interests - hx such as Presidents & battlefields vs. outdoors interests such as hiking & scenery. Don't know your time constraints - can you squeeze Mt. Vernon into afternoon after morning business in NorVA and same for C'ville w/ Monticello? UVA gives great tours of the rotunda - times are listed on their website. Grab a sandwich at Take it Away on the corner and eat lunch - or dinner - on the lawn at UVA. Lots of good restaurants in C'ville and the downtown mall is always fun on a gorgeous summer evening. 2nd suggestion of Michie's Tavern if you are looking for atmosphere but food is so-so. If you are heading on I64W stop at Crozet Pizza which is an local institution and great pizza. 2nd Birdie's recommendation of Wintergreen also. Wonder if your son could spend his time visiting Mt. Vernon or Monticello while you are conducting business and then y'all could head off on a hike together. You may need to narrow it down and concentrate in 1 area, but whatever, you will enjoy.

Momof3boys - thanks for your Mount Vernon and other suggestions. We have seen Mount Vernon (twice) on previous trips. My business is in Charlottesville, so I am focusing more on the northern/northwestern Virginia area for ideas.

Old Rag does not require a parking permit. It is part of Shenandoah National Park so you need to have a park permit. You can self pay the daily fee at the parking lot if you haven't bought one while elsewhere in the park. Unless you're excellent hikers, the hike up Old Rage will take most of the day and it does get crowded (and parking becomes limited) on the weekends. However it's a beautiful hike (and rock scramble). Shenandoah National Park has other excellent hikes, such as White Oak Canyon and parts of the Appalachian Trail. Here are two excellent websites for researching other hikes in the Blue Ridge.
http://www.midatlantichikes.com/va.htm
and http://www.hikingupward.com/

Antietam for sure given your interests...and Shepherdstown is a cute/nice stop for a lunch or dinner and a little wandering. I liked the Yellow Brick Bank restaurant, but that was several years ago.