Hi Chome360,
How big are the trees ?
If they are cuttings they don't need water for 15 days. Just water them normally the day before leaving and voilà .
This is just my 2 cents of the day.
Of course they are yours, and the risk is yours.
I have a growing cutting that is 2 or 3 months old, and it almost doesn't need water .
It has been for a week in front of a sunny window, and still is not droopy ...
I watered another one, and now it is dropping the leaves.... from over-watering !
Of course it depends on your temp in the room and outside. Here outside temps have been ranging from 3° to 20°, not more .
How is your outside temp by now ?