Wow, you have some wonderful responses here. I don't have much to add, except to say that the lure of the comprehensive "canned" curriculum is how easy it will be, yet for HG plus kids, a program like this often needs MAJOR tweaking. The majority of gifted homeschoolers I know use an eclectic approach that is open to change.
BTW, if anyone is looking for a resource for ancient history, my kids have enjoyed online courses at the Lukeion Project. These are primarily about ancient Greece and Rome, and there are 4 week mini courses as well as semester courses. The instructors are a husband and wife with backgrounds in archeology, and they are decidedly Christian, so that influence does come through somewhat. We've only done the minis so far. Dd7 took The Archeology of Destroyed Cities last summer and ds took The Greeks Before the Greeks: The Mycenaeans at age 10.
