I think I found the website regarding the US flag and family reunions. Below is part of what's on the site http://www.reunionsmag.com/gettingstarted/keepingalive_comm.html:

"Descended from a president?

Presidential Families of America is a lineage society whose members have direct or collateral hereditary blood-lines to deceased presidents of North American Republics (USA, Confederate State of America, Republic of Texas, Republic of West Florida). PFA does not do research, respond to inquiries about pedigrees nor provide information about presidents wives, vice presidents or cabinet members. A #10 SASE is required. Send to Dr. Lawrence Kent, 608 S. Conway Rd, Ste G, Orlando FL 32807.

Flags flown over the Capitol

Flags flown over the Capitol building in Washington DC are available to mark extra special events. Expect to pay a small fee depending upon size and fabric. The flag comes with a certificate stating the day, time and occasion for which it was flown — your reunion. You must contact your own representative or senator for instructions.

This was posted by Rose Hendrickson of Park City UT.