“Are there or should there be different creative approaches for different age groups when creating messaging for DOOH?”
If clients have the ability to create specific messaging for very specific audiences, they should. Messaging that is relevant to the consumer would be better received and highly effective.
Day-parting creative would also be a smart approach. Think of a mall. You can run creative geared towards the senior audience that walks the mall early in the morning for exercise. Then, change creative mid-morning for the moms with young kids. In the afternoon, gear your creative towards the students. At night, change to an older adult-focused message.
Speaking to your specific audience makes them much more receptive and allows your space to work harder for you.