How about Eco Straws?
https://www.ecoproductsstore.com/compostable_straws.html
These are compostable and not made from plastic. For Animal Kingdom, you may need to have the packaging on hand to prove they aren't plastic because I have used this brand at various places and they do indeed look like plastic and feel like plastic. Overall, I think they may be a good choice, but as always your mileage may vary. The link I have posted may actually be too many for what you need as that site is aimed towards food service, but it shows they are available. The big difference is I tend to find them to be a bit more durable than plastic straws, but they should not fracture teeth if chewed on. They are compostable and affordable enough to be able to be single use.
There are also compostable flex straws available:
https://www.amazon.com/Repurpose-Compostable-Plant-Based-Straws-Count/dp/B07897C152?th=1
I have not had the occasion to use these particular straws, but they look good and are not plastic.
Once again, Animal Kingdom may be an issue as they look like plastic, so I am truly not sure if they would any of these in Animal Kingdom or not, but it would be much safer for the animals with these around than it would be with stainless steel straws if one dropped into an enclosure.
Also, something that no one mentions about stainless steel straws in that in order to properly clean them you have to use the included brush after every use, which means carrying both the straw and brush everywhere.
This is by no means an exhaustive list, just look enter the following for a search: "Compostable Straws" without the quotes into any search engine or on
Amazon and you will get a very large amount of results, some will be paper and for some reason adding -paper also eliminates some of the ones that look and feel like plastic.
That being said, Disney hasn't said they aren't going to provide straws nor have they said what they are going to provide, just that they will not provide plastic ones.
Hopefully all of this helps someone who needs "plastic straws" going forward, as these would be affordable (at least more affordable than silicone straws, which have their own issues), so if they get chewed through, no big deal, replace it with another. You can even get ones that are individually wrapped if you so desire.
A little off topic, but this has made me wonder, what does Starbucks use in Animal Kingdom for the Frappucinos? You need a straw to be able to drink those and a paper straw wouldn't hold up, so I am assuming they have a solution there as well.