You need to signify whether the child is male or female, therefore "erkek çocuk" would just mean boy, not "man child," although hysterical.
Nominally, the Turkish word for "boy" would by oğlan...
BUT these days it has the connotation of "catamite". I'll leave what that means as an exercise for the reader.
I wonder when it took on that connotation and why. My first attempt at learning Turkish was about 20 years ago, and all of the materials I used translated "boy" as "oğlan" with no mention of "erkek çocuk". I read somewhere that the language has changed so much since Atatürk's first reforms that it can be difficult for young Turks to understand his speeches, because of the difference in vocabulary.