I had a game sometime last month where some kids were wearing referee shirts and big prop glasses during a game where the visiting team was ranked at the time. I got a kick out of it. They were just a group of kids having fun and into their team. Do not penalize the team for the actions of fans. And considering the kids were nice and light-hearted, I had absolutely no problem with anything they did. I even had the AD come to me and ask if I was having any "problem" with the kids. I told him "no, they are just having fun."
You should take this job seriously, but you have to have some fun too.