Greetings Michael:
Sorry to hear about the herbicide drift issue--this unfortunate phenomenon is common here in Illinois too!
Obviously, you need to legally document everything that has transpired regarding this particular case. In addition, you may need to file a report with your state department of agriculture (this is what landowners in Illinois have to do).
Anyways, please contact a local professional consulting forester or a KS state forester for further assistance as you will likely require on-site technical assistance regarding this issue. Ultimately, you could be looking at a lawsuit OR your trees might rebound virtually unscathed with limited or no adverse effects.
Best of luck!