If you can visit them a couple of times a day, that should be fine, I normally see mine twice a day, but sometimes just the once, just to check all is OK ( I can see the henhouse from my kitchen window, and would hear any serious problems), obviously in the winter you would need to make sure that the water was not frozen and like wise that they have not drunk it all in the summer.
An automatic pop hole is the best idea for getting the in and letting them out, I had one for Christmas because I have no close neighbours who can let them out and put them back, but would be able to pop up and feed and water them.