Science fair gives students authentic STEM inquiry, but many teachers lack the curriculum time or capacity to coach every student through the research process. This hands-on AI Playground shows how a structured AI Research Coach can reduce teacher workload while keeping students responsible for their own questions, decisions, and reasoning. Participants rotate through four mini-stations: choosing a topic or phenomenon and drafting questions; using a custom AI Research Coach to refine questions into testable investigations; building variables and hypotheses with prompts; and receiving AI-supported feedback. Participants also examine the AI coach’s instructions, guardrails, uploaded MSEF reference documents, and student scaffolds so they can adapt the model within their own approved AI platforms. All tools and guidance align with Massachusetts Science & Engineering Fair expectations and requirements. Participants leave with science fair-ready templates, prompts, and implementation ideas.