You won't know the ID#
And you don't need to know it.
When and if your son's name is announced they will reference his ID# and then his real full name, position, and where he is from.
Once in a great while a player is announced twice because a team didn't realize he was already selected and off the board.
Based on your comments, it sounds like your son will be in the draft. Scouts should have or will be doing their signability work on your son, especially if he is a potential top 10-15 rounds or better. Though sometimes their signability work gets done without the player even realizing it.