Okay. Yeah, I planned to set out one of those big gravity refill jugs of water and then leave a bunch of hay out.I don't own rabbits, but I have pet-sat a rabbit. Best to have someone come over as frequently as you can afford - once or twice a day is ideal. When I pet-sat, it was twice a day.
Maybe it's just me and my paranoia, but if I had a rabbit, I'd be worried about the water bottle or hay emptying too quickly. If someone is there once a day, it's no big deal. If someone is there every two or three days, they might not be able to correct the problem quickly enough, and unlike dogs and cats, rabbits really don't do well for spurts of time (12 hours max) without food or water.
I'm not sure what you're currently feeding, but rabbits, like all foraging animals, should get concentrated feeds (aka pellets) in quite small amounts more frequently as opposed to large amounts infrequently. I would want someone there to give greens and pellets every day.