An Order of Battle at Friedland 14 June 1807 from G. Nafziger, finds the "Garde de Paris" (2 battalions) in BG Gency's Brigade of Dupas' Division of VIII Corps (facing Friedland, before Heinrichsdorf), unfortunately there is no source cited.
Another of his OOB's for 1 June 1807 similarly places the Garde with Mortier. This time citing Bennigsen's Memoires.
As you've said, he cites Kirgener's "Precise du Siege de Dantzick fait par l'Armée Française en avril et mai 1807," saying the Garde was with the 10th Corps the 15th of May 1807.
As Danzig fell near the end of May, I suppose they could have been in both places...looks as if Daniel has clinched it, however.