If you can automate testing, especially on mobile, I highly recommend it. Building a testable app makes testing easier, whether you actually automate the testing or not.

Mobile testing kind of sucks, automated or not. Manual testing requires an ever increasing number of devices, and the actual testing is slow, monotonous work (aka good testers get bored and move on).

Maybe this approach... Automate what you can, making sure it behaves right. Use manual testing to verify it looks right, and as validation the automated tests didn't miss something.