V.M.
Does he have good receptive language skills? Does he understand everything they are saying? Does he easily follow one step commands? Two step commands? My son didn't speak but his lack of receptive language was really the cause for concern.
Gently approach the subject. While no one wants to hear that there is something wrong with their child, they will appreciate it in the long run, especially if they are able to receive free help. ECI is a great place to strart, but remember that every school district is required by the state to provide free services for children starting at age three who have special needs, including a speech delay.
V.