The tangible interaction approach has, in recent years, become a promising alternative to tactile interaction for very young children. Children playing with Tangible User Interfaces (TUI) are motivated by the novel and digital environment and benefit from the same values as conventional physical playing. Young children build their mental image of the world through action and motor responses and, with physical handling, they become conscious of reality. Within TUIs, digitally augmented surfaces (interactive blackboards and tabletops) are becoming popular in educative environments. Tabletop devices are horizontal surfaces capable of supporting interaction and image feedback on their surface, and are especially interesting for reinforcing face-to-face social relations and group activities. However, most of current children-oriented applications for tabletops are based on tactile interaction, thus losing the benefits of physical playing. The paper describes our experiences building tangible tabletops, and designing tangible games and toys. In particular, we present NIKVision, a tabletop device intended to give leisure and fun while reinforcing physical manipulation and colocated gaming for 3-6 year old children. Several hybrid (physical/digital) games based on the manipulation of passive and active toys have been developed for NIKVision. From our experience several useful lessons can be extracted. Among them, the necessity of bridging the gap between designers and developers making it easier the prototyping of tabletop games stands out. To tackle this difficulty a toolkit for the prototyping of tabletop games called ToyVision has been created. The toolkit supports designers to fully explore the physical feasibilities of the manipulation of physical playing pieces, while minimizing the technical difficulties of implementing tabletop games based on physical manipulation. This way, NIKVision and ToyVision are becoming powerful tools to develop innovative serious games.