You should be able to limit the water flow with the tap's isolation valve. So long as the water isn't coming out too fast it wouldn't be wasting that much water

You should be able to limit the water flow with the tap's isolation valve. So long as the water isn't coming out too fast it wouldn't be wasting that much water compared to running a bath, for example. Not sure how you'd go about recycling the water though. Do you think they would be interested in an indoor water feature? That could be an option.