Damage? Probably not. As long as even a trickle of water flows through your pump and filter, it will be fine. Centrifugal pumps are overloaded by high flow, not low flow. (No flow will boil the water and cause other problems, though.)

Huge mess? Yeah.

If your son can't be there consistently, you are pretty limited in options.

Given your schedule, once you get back you can start working on it. It would help if you have a K2006 testkit (Amazon link in sig) and, if you have a cartridge filter, a new filter cartridge both waiting on you.

Do NOT use more algaecides and stuff -- it will just make it harder.

If your son can dump 6 - 8 gallons of PLAIN 6% household bleach in, every time he comes over, that will lessen the problem when you return. But, tell him NOT to wear his expensive uniform when doing so -- bleach seems to jump out and touch you, anytime you wear anything nice.

Good luck.