Well, there are the detailed entries in Orville Wright’s diary of 17 December 1903:
Wright Brothers Information Packet Primary Sources: Orville Wright's December 17, 1903 Diary Entry - Special Collections & Archives - Wright State University Libraries
His diary states that the following five men helped the Wright brothers and, thus, were witnesses to the 17 December 1903 flights:
1.
John T. Daniels (a USCG Surfman at the Live-Saving Station at Kill Devil Hills, and
the man who operated Wilbur Wright’s camera)
2.
Adam Etheridge (another Surfman)
3.
Will Dough (another Surfman)
4.
W.C. Brinkley, a farmer from nearby Manteo, NC
5.
Johnny Moore, a 17-year-old from Nags Head who was visiting the life-saving station
I’m sure you’ll unreasonably jump on the word “only,” but here’s an article from 2003
Only five witnessed Wrights' first flight - Technology & science - Science - Tomorrow's Wright Brothers | NBC News
This article, from the United States Coast Guard site, understandably, focuses on the participation of the Surfmen:
The Indispensable Men: USLSS At Kitty Hawk, December, 1903