Research suggests that dialogic reading and wordless picture books may improve narrative production and comprehension leading to better school readiness. We aim to understand children's experiences using a wordless picture book scaffolded by audio prompts. We designed, implemented and assessed the Spring-a-story web app with 35 children aged 3 to 6 in a socio-economically-disadvantaged area in the UK. We sought to comprehend to what extent the application supports children in creating a narrative, and which type of prompts (basic dialogic reading and theory of mind prompts) better support their meaningful responses. Initial findings suggest how children were able to respond meaningfully to prompts and reported high levels of enjoyment of the activity. Furthermore, theory of mind prompts resulted in a marginally higher percentage of meaningful responses and theory of mind language compared to basic dialogic reading prompts. Study outcomes helped to delineate the design space that we shaped into six design challenges that aim to inform the community and guide the future design of tools to support children in independent dialogic reading of wordless picture e-books.