Hi Katherine,
Welcome to the Disney Parks Moms Panel and thank you for asking us a question.
You’re absolutely right to note that, according to the
Walt Disney World Resort Park Rules, balloons and plastic straws are not allowed at
Disney’s Animal Kingdom Park to ensure the safety of the animals that live there. However, I don’t see anything in the Park Rules against brining in any other kind of reusable straws made of silicone or aluminum. Plus, I think it might even be possible to bring clearly reusable plastic straws, provided they're clearly not the same as a disposable plastic straw (i.e. not meant for a single use), but please note that they might get confiscated by Park Security if they choose to follow the Park Rules to the letter.
I would also recommend that you err on the safe side and avoid any glass containers, or straws, as glass food containers (even small ones) are clearly on the “prohibited items” list for all of Walt Disney World Resort’s Theme Parks and Water Parks.
I hope my answer helps you plan your upcoming visit. Please don’t hesitate to come back and see us if you have any other questions.
Have a Magical Day,
Lynne