Informed by literature on childhood expertise in high-interest topics and parent-child conversation in museum settings, this study explored how children's level of dinosaur expertise influences family learning opportunities in a natural history museum. Interviews identified children with high and low dinosaur knowledge and assigned them to expert and novice groups. Parent surveys revealed that expert children were more likely to have home environments where family members shared interests in dinosaurs and provided a variety of dinosaur learning resources. Analysis of family conversations demonstrated that parents with novice children "more" actively engaged them in learning conversations than parents with expert children. The implications of this shift in parental engagement are considered in terms of interest and knowledge development in informal settings, highlighting how "islands of expertise" might facilitate and in some cases hinder learning through shared family activity. (Contains 4 tables.)