Great Googly Moogly!
3rd and 4th grade teachers, now that you are proficient in Google, have you considered Google Classroom? You can have students sign up using a class code. Students can receive and turn in work through Google Classroom. You can also have discussions using the thread.
Student Digital Leaders- SeeSaw
One of my librarian friends just told me about this great app! It allows students to take pictures or video their work and upload it for the teacher to view. You can also invite families to view the student work. This may be a great answer for K-2 students since they don't have Google accounts! Let me know if you would like this on the iPads.