This paper describes a new interaction paradigm for handheld computing: the use of multiple interconnected devices to form a virtual shared workspace. Given the importance of rich, social interactions of children, we wanted to explore ways to effectively support children's collaboration on handheld computers. We investigated the notion of distributing shared information across handheld displays by applying user-centered design techniques for children. Based on these ideas, the WHAT-IF feature was developed to extend Geney, a collaborative activity for handheld computers where children can explore genetics concepts. The WHAT-IF feature facilitates children's synthesis of information and discussion during the collaborative activity. We then conducted an exploratory study with seven 7th grade participants, observing children's use of this new interaction paradigm, and gaining feedback on the WHAT-IF feature. The results of this work illustrate the potential of handheld computers for supporting children's social interactions in collaborative learning activities.