Quiz Application

I need help creating a modern and user friendly quiz application. The application should be kids-friendly and should be used by the children easily. I will have multiple categories. The type of quiz I'd like to create is multiple choice. Additionally, I would like this application to include images and/or video as part of the quiz. However, I don't want a time limit to be included for the quiz. The data would be in JSON and should have InApp feature for both iOS & Android. I'm looking for experienced professionals to work on this project and ensure a high-quality end result.