If your around periodically during the day i would just use a hand sprayer and spray a few times a day. If your gone the whole day, i would get a pro mist.
With 3 chameleons I would say get an automated system if you can afford it.
They are awesome!
If you have to sit there and spray each cage for 5 minutes 3 times a day that equals 45 minutes a day of hand spraying.
I dont mist for longer than 30 seconds twice a day when i do it by hand.
I have upgraded to a PM and it is really worth its weight in gold.
just allow the water to dry be4 the next misting.
Better yet, drill some holes on the plastic bottom and put some kind of a good drainage system so the water falls to a bucket below.