There is nothing wrong with having a little fun while doing your homeschool thang! It not only helps to let off steam that you or the kids have built up over the course of the day, it also helps to create memories! How many kids do you know who will remember how their parent played hide-and-seek with them right before Grammar lessons!?
I realize you are just starting out your year and your new "school" schedule, and it probably doesn't include "fun time". Well my advice to you is don't put it in there! Wake up every day and tell that task master in your head that fun will happen even if she tries to schedule around it!
You are a unique Mom with a unique opportunity to make unique memories! Do it and have fun!