@Mike1034 I think @Beth80 has some great suggestions there. I use waterproof mattress pads that basically have two layers - the waterproof one on the bottom, and the soft, fuzzy one on top. If you don't mind spending more, you can get a thicker pad with a quilted top, but these are harder to wash and don't hold their shape so well over time. Either way, the waterproof cover doesn't really change the way the mattress feels, as long as you have a good fitted sheet on top of it.
I don't know what's up with kids these days and their incontinence. But ok, if you're having Silicon Valley interns as guests, maybe their working conditions are so bad that it screws up their bladder health. Or maybe they're experiencing alcohol or drugs for the first time. At any rate, I don't think it's worth mentioning in a public way unless you have good reason to believe the guests actually intended to wet your bed. You can request payment in the Resolution Center, as long as you have solid documentation of the costs, and can countenance whatever reaction the guest has to the embarrassment.
If you do choose to seek compensation, that would be the only reason to send a private message about the stains. Perhaps the angle would be to ask if there were any issues obstructing their access or comfort in the bathroom facilities. Personally though, I'd find that much too awkward. Best way forward is just to make those beds as guest-proof and bodily-fluid proof as possible.