Whoops! Sorry, I didn’t look at your plans!
Shutterbuttons is a video that you and your family can do at a store in Diagon Alley. You stand in front of a green screen, and the photographer narrates a scene. When it is all said and done, you get a video that looks like the moving pictures from Harry Potter. Here is a link to the one my family and I did so that you can see what it’s like. It is kind of pricey, but an amazing souvenir for HP fans. https://photos.app.goo.gl/vC9UR6WfbmTgbo4I3
As for Forbidden Journey, the last time I went, I just went through the standby line and tucked myself into a corner in any room where I wanted to see a full show. People just moved around me without any problem. I don’t think it’s necessary to do a separate tour, and I’m not entirely sure that it’s available all the time, either. If at any point, you decide to get Express Pass, be aware that the Express Pass line bypasses quite a bit of the castle and you will miss a lot.