According to relevance theory, communication relies on speakers’ ability to signal relevant information, which addressees use to infer meaning efficiently. Most research within the relevance theoretic framework has examined how relevance is marked in speech, treating it as the primary channel for signaling informative content. Yet, little is known about whether, how, and in what contexts speakers highlight information in co-speech gestures. Here, we investigate how speakers use ostensive cues—specifically, visual and verbal deixis (e.g. gaze toward a gesture, demonstratives like “this,” “that,” or “here”)—to highlight the communicative relevance of iconic gestures in child- versus adult-directed communication and whether addressees show sensitivity to these cues. Sixteen Italian adults explained the rules of two logic puzzles to a child and another adult. Results show that speakers highlight more gestures for children than for adults, primarily by using visual deixis. Furthermore, addressees of both age groups, adults and children, were more likely to shift their gaze to highlighted than to non-highlighted gestures. These findings demonstrate that speakers dynamically adapt multimodal cues to highlight iconic gestures for addressees, providing empirical support for extending relevance theory to a multimodal view of language.