James Rogers McConnell was one of Kiffin's closest friends during their time at the front in 1916. He and Kiffin used to listen to many songs on the phonograph given to the squadron by Charles Prince. They and the other boys especially liked "When that midnight choo-choo leaves for Alabam'" and "The Old Maid's Ball."
Kiffin loved and admired Victor Chapman. Following Victor's death (in June 1916), Kiffin wrote Victor's mother that all the boys had felt her son's influence on the squadron, "and seeing in him a man made us feel a little more like trying to be men ourselves." This site has some great information on Victor, and a wonderful video where you can see Kiffin and the other boys in the escadrille.
Alan Seeger was in Kiffin's squad in the Foreign Legion, and was with Kiffin one fateful night at a battered barricade in a ruined chateau in Craonnelle, France. Perhaps that night inspired his famous poem "I Have a Rendezvous With Death," which begins: "I have a rendezvous with death, at some disputed barricade...."
Kiffin (second from left) had many days of hard work while in the Foreign Legion. In one letter he sent to St. Elmo Massengale, his former boss in Atlanta, Kiffin explained how busy he was by referencing a song made popular a few years earlier by Billy Murray, "Nothing to do until tomorrow."
"Decoration Day" was celebrated in the Place des Etats-Unis on May 30, 1916. In this video, just after the 54:00 mark you can see the days' events, including William Thaw with his wounded left arm still in a sling (far right, 54:54), George Leygues giving his well-received speech praising the American volunteers and the wreath-covered statue of Washington and Lafayette. Here is a good reading of Alan Seeger's poem written for the day, "Ode in Memory of the American Volunteers Fallen for France."
On 4 Juillet, 1917, Paris officially welcomed General John J. Pershing and the American troops to France. This link has some good footage of the days events, including the march through Paris and Colonel Stanton's "Lafayette, we are here!" speech at Picpus Cemetery.