After listening to the Hamilton soundtrack a bit, I got to thinking about the Revolution in general. It wasn't exactly a secret who was in charge and where they lived, so why did the Royalist forces not capture the estates in question?
Monticello was raided in 1781, and the British came fairly close to capturing Jefferson, who was the governor of Virginia at that time.
Occupying Monticello would have been difficult, since British troops were thin on the ground in the southern states. Garrisons far from their naval power were particularly exposed to counterstrikes by local militia, once the militia had time to organize themselves.