Before I moved to my current house, I lived in a condo. Here's the rig that I created for getting my Vandas through the winter. In the spare-bathroom shower I rigged a "sprinkler" system over the plants, with a submersible pump in a 5-gallon bucket (which held enough water for a week), and a timer that would turn on the pump for a few minutes on my selected days. I also included a big metal-halide light since they lived in that environment for several months. If you are just covering a vacation, don't worry about getting the light just right, it isn't all that long. A suitable timer might take a little searching but the other parts of the "sprinkler system" are simple.
http://orchidcentral.org/GrowingAreas/Vandacity.jpg