Though prior work shows parents worry about screen media experiences displacing physical activity and time outdoors, this research does not account for location-based mobile games like Pokémon GO, which specifically facilitate outdoor activity. To fill this gap in the research, we surveyed and interviewed parents to understand (1) their values and perceptions of this type of gameplay and (2) how they co-play Pokémon GO with their children. Our findings provide empirical evidence that, in addition to appreciating the increased exercise and time outdoors, parents valued how play led to family bonding experiences. Furthermore, some traditional concerns about screen time persisted in this context, and new concerns about safety in real-world environments emerged. Parents mitigated these concerns with rules and gameplay choices, such as maintaining control of the mobile device, to ensure children were safe. This work contributes an empirical understanding of families as co-users of technology and offers a generative lens to study and design for joint media engagement among family members where gameplay differs from normative notions of screen time.