I have 4 iPads. I am a non-profit organization. Can I use the same Apple ID on all 4 iPads?

Can you use the same Apple ID? Yes.

Should you use the same Apple ID? Absolutely not.

Get started using Apple Business Manager or Apple School Manager with Mobile Device Management - Apple Support

You sure can. Just remember, as far as Apple is concerned, you = your Apple ID.

So as long as you are the only person using those four iPads, you're ok.

If those devices will be shared with others, not ok.