First off, cooler temperatures helps cut down dramatically on mold and fungus outbreaks. You just set it on a temperature a couple degrees cooler than the outside air and leave it on continuous run. Since it's not that hot outside, the compressor will only kick on once or twice per hour, so the bill wont be that bad.
All a dehumidifier is in reality is an AC unit that works in reverse. You might as well get some cooling to go along with the dehumidification an AC unit gives you because once you lock up all those lights in a room it'll get pretty damn warm in there pretty damn quick.