I meant Yosemite Falls on Yosemite Creek. From Half Dome I assume the plan was to drop to the camp on Sunrise Creek. Next day drop to the valley via either JMT or Mist Trail (Nevada and Vernal Falls). By going up Yosemite Falls the same day, I assumed they meant to take the shuttle from Happy Isles to Yosemite Falls TH and go up that trail that is next to Yosemite Falls. At a certain distance from the rim camping is legal along Yosemite Creek. Of course, this only works when Yosemite Creek is running! Mid June this year should be fine. Doing the Half Dome climb the same day as going all the way down AND up Yosemite Falls would be quite an energetic day! I would say that mid-June there is enough daylight to do this, but you would have to be in great shape.