As part of an international collaborative design-based research initiative, this study examines the applications and perceptions of generative artificial intelligence (Gen AI) among pre-service primary teachers within an Irish educational program. It focuses on how personal and academic uses of Gen AI influence their perceptions of using Gen AI for lesson planning. The findings highlight that while Gen AI is preliminarily used by pre-service primary teachers for personal and academic purposes, its integration into lesson planning is less frequent. Crucially, the study reveals no significant correlations between personal use of Gen AI and perceptions related to its educational opportunities. Conversely, academic use of Gen AI shows a positive correlation with recognising its potential opportunities for lesson planning and the desire for professional development, but it also shows a negative correlation with the perception of challenges and ethical concerns. The research underscores substantial concerns about over-reliance on Gen AI, potential skill diminishment, educational equity, and data privacy. These findings emphasise the urgent need for targeted professional development programmes to prepare future teachers to use Gen AI tools effectively and ethically, highlighting a gap in current teacher education that must be addressed to harness the full potential of Gen AI in education.