Good (free or cheap) video editing software
Good (free or cheap) video editing software
The title clearly states the project, and it’s great that your nephew is excited about his Nerf guns and wants to create a video with effects like explosions and blood using a simple editing tool. Thanks!
Adobe Premiere Pro and After Effects Pro. Otherwise, Final Cut Pro X (or the alternative they offer)
I recommend trying HitFilm (free version) to become comfortable, though I’m unsure how its interface differs from Adobe. Since you already have Adobe Creative Cloud, you’re familiar with it. It seems the choice is between HitFilm and Adobe—HitFilm is often praised as the top free option.