Replacing Zombies with Farm Animals

[CaptainCalzone]

Hey everyone, I have an "entitygroups.xml" question. TL;DR version is in the title.

 

My girlfriend and I love playing this game, but she's easily frightened and hates the zombies. Until the latest update that was fine, we'd just turn off zombies and play. But now even with that setting we've encountered hostile dogs while exploring. While looking around for a solution we discovered the "entitygroups.xml" file and all the fun stuff that comes with it. We were wondering if there's a way to replace the zombies with chickens, pigs, etc. All of my attempts to mess with the code myself has resulted in "object reference not set to an instance of an object" errors popping up when I enter buildings. Any ideas?

 

Thanks in advance!