You might consider using a storyboard to help kids organize their thoughts and ideas beforehand. Since this was their first time using Sock Puppets, we let them have less structured time to play and learn. Once the videos were finished, the kids saved to their camera rolls and uploaded to Seesaw. It worked great!
The app is free, and offers in-app purchases. I think using what's included in the free version is just fine. Encourage kids to use their imagination and creativity and make it work! In-app purchases don't transfer to other iPads, so you'd need to buy it for each device. Boo! It's pretty user friendly, but if you feel you need help, there is a great tutorial on YouTube:
Here is an example from Ms. Oringer's room. So fun! Let me know if you decide to use this app. I would love to see what you create!