Children's museums are delightful, whimsical, and joyful places, but they are undertheorized. This limits our capacity to fully leverage children's museums as spaces for expansive visions of literacy learning. It also limits our examination of the potential harms enacted by children's museums. To theorize the children's museum, I take Ash's framework for reculturing museums as a starting point. Using Cultural Historical Activity Theory (CHAT) plus critiques of neoliberalism and deficit logics, I argue that children's museums are complex activity systems that aim to negotiate the literacy-related objectives of families, schools, and other sites of learning. Neoliberal ideologies and deficit logics inform these negotiations. I analyze two contradictions: (1) between the mediational means of play and the objective of learning, and (2) between the rules/norms of children's museums and the diverse communities they serve. To close, I reflect on potential pathways for reculturing children's museums toward more justice-oriented practices.