Research on the impact of guided investigation, including verbal guidance strategies, has expanded in the recent decade, and the current work contributes to this line of research in a museum context. The current in-depth study examines the impact of verbal guidance strategies on family learning at an open-ended museum exhibit, considering participants' individual characteristics. The experiments and conversations of 104 families were observed at an object motion exhibit. Results show that families, with and without guidance, investigated in a meaningful way by performing control-of-variables strategy experiments, investigating a range of variables, and formulating hypotheses and causal explanations. However, the results also show that the process of learning scientific concepts could be improved. Minimal interventions of museum educators positively affected the families' learning process by reducing the number of scientifically incorrect remarks. Interestingly, in addition to discussing the phenomenon, especially the families with highly educated parents discussed the topic of reliability of their experiments, which is an under-investigated aspect of learning through investigation. Only children's cognitive ability and not parental education was modestly, but consistently related to the families' performance.