Good job.
Though not without its flaws, this is a very enjoyable "cute spooky" (in a good way) movie, with an interesting concept and plot, nice (albeit rushed) artwork, and the fact you got your nephew to voice the trick-or-treater at the end is a really cute addition too.
However, there wasn't much animation, mostly special effects I could've done in OpenShot or some other video editor. I know you only had a week to finish this, possibly less, so I can mostly forgive this.
I also found the voices painful to listen to: it keeps clipping, especially when it's loud. The laughter and at the very end, the "or DIE" bit are both very good (or bad) examples.
Your voice is good, and your nephew's didn't clip at all, but for future reference, consider paying attention to how much the audio is gaining during recording, use a limiter, and balance things up in post-production.
Audio Engineering 101: Audacity has everything you need to make sure everything sound consistent and crisp.