I wouldn't be so concerned about feeding so long as you feed them with well gutloaded feeders the day you leave. Chameleons can go for up to a week without food so if you are only away for four days, they will be fine.
I think my main concern would be about their hydration and where it was coming from. Four days without water would be a huge detriment to your chameleons health.
Do you have a misting system that can support a four day absence?
I agree, chams can go a week without food with little to no issue. The temps and lights are another issue, so is the misting. If you have a timer and a mistkit, then you are green to go. If not, then set up a ceramic bulb, put them by a window, and get a gallon dripper with a real small hole that drips once every 10 sec or more. A gallon holds about 90,000 droplets...that's good for 250 hours or so. That gives you like ten days, give or take. Good luck dude.
i wouldnt leave them in the house alone for that long, you have to think about the humidity too. i would leave your chams at a friends house to play it safe. and you also have to turn the light out at night so it can sleep. plus youd want to make sure its healthy while your gone so that would help to. i always leave my cham at my friends so they can take care of it because my chameleon would never survive that long alone.
I'd leave a handful of crickets in the cage.. Some people say not do leave crickets in overnight because they can bite your chameleon, but if your cham is not a baby, I'd say don't worry about that. Let's not forget who's the preditor here
That aside, lighting and misting are HUGE factors.. Do you have an automatic/timing system?? If not, you have an issue. To handle the water, you can put a dripper on top of the cage.. just get a liter, poke a hole or two in the bottom, fill it with water and set it ontop of the cage... Lighting, on the other hand, won't be a fixable issue unless you can have a friend come in and turn the lights on/off for you.
I highly recommend getting a misting system like the MistKing if you don't have it already.. Also get your lights on a timer, that way you won't have to worry about future trips out of town like this one
Quickfix, go to Lowe's, Orchard Supply or wherever and buy a $15 timer.. Connect your lights to it and set them at 10-12 hour intervals.. Do that, setup a dripper like I described above, throw some crickets in the cage and your cham will be perfectly fine