If it was me, I would price AAA-BBB-AAA and AAA-CCC-AAA and bill each client that amount.
Then book whatever you need. If you come out ahead by doing a multi city segment, that's part of your fee as a consultant.

The client in BBB has no business knowing where you are going next, and CCC has no business knowing where you came from. Nor should either be subsidizing the cost of your travel for the other one.