The latest version of the Google Keep app for Android lets you export your notes to Google Docs, just like the desktop site. Open a note, tap the menu button and pick "copy to Google Doc".
You can also select multiple notes and use the same feature to export your notes to a Google Docs document.
If you don't have the latest version of the Google Keep app yet (3.1.313), you can download the APK file from APK Mirror. According to Android Police, "the APK is signed by Google and upgrades your existing app".