I don't know about you, but I find hard copy books much easier to read than online copies (which sucks as they go out of date quickly).
You could buy several books from O'Reilly.
I also recommend buying The Phoenix Project it's a fictional account of dev ops. An easy and silly read, but good to start a conversation around cultural improvement.
A frame challenge
Don't spend the money just for the sake of it, just because it exists in the budget (just as you wouldn't in your personal life, I expect, if you happened to get an unexpected windfall! You wouldn't say "I received this $200 from an unexpected contractual penalty (or whatever) so now I need to spend it" would you?) I get the feeling that ...
So your budget resets in three weeks. What you're looking for then, is things that can be paid in advance. That should be doable; most companies, including educators, are happy to take money early.
So what are good kinds of professional development to spend it on? I would look at:
What else do I need to consider when making the decision whether to help them out?
What I'm missing in your thoughts is whether you are qualified to do this. Can you teach a college class? Having the knowledge that is taught does not mean you can automatically teach it. Teaching is not just standing there, randomly rambling about knowledge you have. It is a ...
Honestly this sounds like a great opportunity. I can think of some big pros
Learning - Teaching is a fantastic way to find out what important things you don't know, and consolidate the things you do know. You can think you know a topic really well, come to teach it to others, and find out you really don't. You learn a lot going through the process. Doing ...