Hiya Jayla!
Welcome to planDisney! You can definitely take bags into any of the theme parks at Walt Disney World Resort! In fact, I have a list on my phone labeled "Park bag checklist" to help make sure that I have everything I need in that bag.
There are
rules about sizing and what you are allowed to bring but as long as you follow them you are set. The bag cannot be larger than 24" long x 15" wide x 18" high. If you get tired of holding that bag in the Parks, you can
rent a locker for the day to keep it safe until you need it again. There are lockers in each of the Parks that are usually located near the entrances.
I suggest trying to be as minimal as possible as you will be constantly taking it on and off when boarding attractions. Make sure that if you are wearing a MagicBand+ you take care to make sure you don't lose it. It's always when I take on or off my backpack that my band snaps off. The panelists here at planDisney have gathered a
Park Bag must-have list and I hope that it helps you! I see that you want to visit in December! The last time I visited the Parks in December I was shocked at how chilly the mornings and evenings were. Having a light sweatshirt in my bag was very helpful for those times.
Have a great trip and enjoy every minute!
Happy Planning!
-Nimmy