I join rickair's recommendation to have them consult with an aviation attorney. Whether aviation or any other type of business, especially a regulated business, part of the cost of operations should be a compliance consultation of some sort.
That said, for general information, it sounds like you have a general handle on the potential applicability of Parts 380 and 298. Here's a 2011 Chief Counsel interpretation that while it may or may not be directly applicable to your specific situation, discusses some of the considerations (check the footnotes):
http://www.faa.gov/about/office_org/...rpretation.pdf