Of course you can bring them in!
You may have to be a bit "sneaky" about it, but seriously....CM's at the gate have way too many folks to screen and just don't care too much about items like this.
They are looking for weapons, drugs or other harmful items- like glass bottles.
I always bring in a big cooler full of outside food and soda and I've never had any issues. Of course my cooler is NOT a wheeled one and I have no glass bottles, both of which or clear "no-no's".
I would suggest burying your items at the bottom of a largish (10-12 can sized) cooler and if you have a stroller, just strap that thing on the back of it. They will ask you to pull the cooler or backpack off the stroller but have never actually emptied everything out and even dug to the bottom of ours. They usually just want to confirm that yep- there's really food in this cooler and nope, there's no glass or weapons.
Several CM's even complimented me on how smart is was to put our chocolate (I brought organic choc muffins in for breakfast) inside the cooler to keep it from melting into brown goo during the summer heat.
The only issues that I can think of you having are of CM's stopping you from playing the instrument or games out of confusion/distraction to other guests. But if you're quiet about it- really....they don't care!
It's not like your going to be walking down Main St. playing an impromptu concert, right?
