We present an evaluation of three prototype tangible user interfaces (TUIs) for preschoolers during mealtime. Building on past work identifying value tensions between adults' and children's perspectives at meals, we examine how the TUIs address different tensions in this context (for example, the tension between children's interest in experimenting with food versus adults' interest in cleanliness). Thirteen preschool children and their parents tried out the prototypes, as did an additional seven preschool teachers. Adults and children alike were excited by the prototypes; parents were surprised by children's increased food intake, and children used the prototypes to engage in artistic expression with food traces. We also found that the prototypes motivated children's increased consumption, sometimes displacing their own hunger cues. We conclude that TUIs have the potential to enhance shared meals between children and adults but also have the potential to distract or persuade children in inappropriate or harmful ways. We present design guidance differentiating these two outcomes, such as incorporating the TUI into pre-existing mealtime objects and routines.