I heard in our Shiur that it could mean, "Don't make your sons like daughters," by not practicing the Mizvos designated for a son which a daughter is exempt of doing.

Regards,

Shabtai Nacson, Toronto, Canada

See Meiri there, who suggests a similar interpretation.

["...an additional interpretation of this Gemara is, woe to the person whose sons are lacking and not fulfilling their role, happy is he whose sons are filling the role they are supposed to."]