Children with Autism Spectrum Disorder (ASD) face several difficulties in social communication. Hence, analyzing social interaction can provide insight on their social and cognitive skills. In this paper, we investigate the degree of engagement of children in interactions with their parents. Features derived from both participants including acoustic, linguistic and dialogue act features are explored. The effect of visual cues is also investigated. We experimented on the task of engagement detection using video-recorded sessions consisting of interactions of typically developing (TD) and ASD children. Results show that engagement is easier to predict for TD children than for ASD children, and that the parent's actions/movements are better predictors of the child's degree of engagement.