branched drain system to irrigate pasture

We are setting up two RV campers to use as airbnb housing about 150 feet from our house. We plan to run electric from our own house, but we would like to store water and fill it up with hoses instead of running water lines out there too. But my real question is on grey water draining systems. The campers will be about 10 feet from a pasture we use for grazing sheep(gentle slope downward from the camper site) I was hoping we could do some sort of simple branched drain system to irrigate that field. Any experience or ideas? It would be great for it to be low cost, since other aspects of the project are more costly. also, we are planning on composting toilets, so we will have no sewage to deal with, just grey water. Thanks!

I have seen what you describe many times. One smart thing to do is shift the pipe end from time to time.
What is happening to the urine?

Taylor Cleveland, what did you decide? I've got a similar situation where I could do that but it gets cold here so I'm not sure about the outlet freezing? What do you think John C Daley? And what about keeping critters out of the pipe - lots of snakes here!!! Any pics or drawings about plumbing this to the house? I like baths so what happens in winter, is the water bad for trees in winter?

And the trees I need to water are up a gentle hill (10' - 20' rise)from the house. How do I deal with that? Will I need a holding tank and pump? Or?