I definitely agree with the comments from gvdIAD. Ash Lawn is so different from Monticello. And Montpelier is splendid too.

If you have the opportunity to tour UVA the day before, definitely try to take one of the free tours. The University is beautifully designed, and the serpentine gardens for some of the residences quite lovely.

The Bayly Art Museum has some excellent exhibits. I'm not sure if it's closed for renovation, though.

Have a good time.