While there are growing calls to involve end-users in designing AI, the limited understanding of AI's capabilities among the general public hinders their effective participation in AI co-design. This study aims to facilitate the participation of non-technical audiences in AI co-design through the development of a card-based AI literacy toolkit. The toolkit was designed (1) to inform users about AI by presenting 16 competencies extracted from the AI Literacy conceptual framework by Long and Magerko (2020), and (2) to support idea generation and questioning about AI through "What if?" prompts, as done by designers. The effects of the informative and generative toolkit were assessed using a mixed methods approach. First, its impact on AI literacy was evaluated in a design task where non-technical participants (N=50) generated questions about future AI systems. Results showed a statistically significant increase in critical feedback, breadth, and frequency of AI-related keywords in participants' responses after using the toolkit, indicating improved AI literacy. Second, the effects of the toolkit were examined in a co-design workshop involving a group of six participants, half of whom without an AI background. Post-workshop interviews revealed positive effects on collaboration, including the development of a shared vision and common ground within the group. Both studies highlight the potential of AI literacy in enhancing the participation of nontechnical audiences in co-designing AI with practitioners.