From the Nashville City Paper:
In its first few seasons, Nashville participated in a prospects tournament in Traverse City, Mich., with several other franchises. Last season, two rookie games with Atlanta were held during the first week of training camp.
Trotz said any rookie camp this year would include reciprocation on those two games with the Thrashers’ prospects, this time in Atlanta.
Last year they were around Sept 23, which was after the start of training camp. If you're going to do them earlier, it would be around the same time that the Traverse City tournament is going on.