This study compared traditional rugby union (RU) games to a modified small-sided game (SSG) aimed at improving opportunity for physical activity and enjoyment in children. Twenty-six school rugby players (aged 10 y) played 10 RU matches. Five traditional games on a full-sized field with 10–12 players per team and five SSG on a modified field with seven players per team. Movement patterns, enjoyment, involvements (e.g., possessions, passes, tackles, rucks and tries), and heart rate (HR) were recorded. Session rating of perceived exertion (sRPE) was measured at the end of each game and used to calculate game load (sRPE x duration). Significance was set at p ≤ 0.05. Individuals covered greater distances (total, low and high speed) overall and relatively (per min) and had higher HR whilst playing traditional format RU. Despite covering greater distances, perceived exertion and game load were similar and importantly, enjoyment was high for both game formats. Individual player match involvements (overall and relative possessions and passes, and relative tackles) were higher in SSG. Given that players enjoyed both game formats, movement pattern and physiological data suggest traditional games may be more suitable for improving physical activity and fitness, while individual involvement data suggest SSG may be more suitable for improving opportunities for participation and skill development.