make sure they are all in cases, and the cases are closed tight. That way when the AC comes back on, the speed of the drop in humidity won't be too rapid.
Also, if you have multiple floors, put them up on the top floor where there is less humidity.
Mold grows above 65% very quickly. So if you really are at 80%, it is pretty imperative that it gets repaired quickly.
You might want to just go to Walmart or whatever and buy a cheap small dehumidifier and put it in your smallest room and put the instruments in there with the door closed.