App Build CMS

We need help building an educational app that includes text, matching audio files and sometimes image files. There will be thousands of screens, all structurally identical with minor variations. These screens will occurr within a clearly defined taxonomy/sequence and user progress must be tracked. There is no video or animation. The app must support a few basic revision exercises for content--built around simple question types (fill in blanks/rearrange word order, etc.) We will release a series of apps on the same code base and we want to use/purchase/build a codebase that enables us to build multiple apps, populating them with content through a basic Content Management System (CMS). We also need a designer to work with us on the visual appearance of the app and its related brand—we have clear expectations and a clear aesthetic already. We will be building a freemium version of the app with, initially, one upgrade to unlock the full content and future upgrades to add additional content of similar varieties--a successful applicant can expect to be retained/reengaged for a maintenance/expansion of the app family. We want to build simultaneously for Android and iphone and we want to incorporate industry standard ad services (adwhirl) from the beginning. We want to begin building in mid-June and be ready for launch by mid-August.