The left telescope is the Harlan J. Smith, the one we took a tour of, and I don't know what the right one is called. They sit on a mountain that's a significant drive away from the main building of the observatory (where they have presentations for tourists, a cafe and star parties). Interestingly, at the telescope they have WiFi for public use, but in the main building / visitor center they don't have any. Cell phones don't work there either, since the observatory is so far from the rest of civilization that the cell signal is weak-to-nonexistent there. To be fair, there is hardly any cell phone signal anywhere in West Texas, except in its towns. The areas between towns has no coverage. The ranch where we stayed has no coverage either -- and somehow people manage to live there...
McDonald Observatory star parties take place in a big, circular outdoors square near the visitor center. They start at twilight. At first there is a presentation, during which the presenter points out some interesting objects in the night sky that can be seen with a naked eye; at the time we were there, one of such objects was Mercury. "Only 1% of the Earth's population have seen Mercury in the sky," said the presenter, adding that a lot more people may have seen it, but didn't realize it was Mercury. "So all of you now are part of the 1 percent. Maybe not THE 1 percent you want to be part of, but a 1 percent."
While the presenter talks, it gets completely dark. Then people can observe the stars through the smaller and bigger telescopes that are set up all throughout the area surrounding the square. The bigger telescopes are in tent-like structures, the small telescopes are set up right there on the pavement. It is pitch-black dark, since no one is allowed to use flashlights or glowing phone screens. This is so that your pupils (that have expanded to see the dim starlight), won't shrink again if someone turns on a bright light near you. While it's the right approach, it makes it very difficult for a group to find its members if they separate. There were 6 of us, so... a small comedy of errors happened.
The night we were there, all the telescopes were pointing to a tiny patch of the sky in the Orion belt, where new stars are still forming. I wasn't sure why the observatory made the choice to point all telescopes to the same spot, and whether this is typical for star parties. I would think it would be more interesting if you could observe several areas of the sky. In any case, on that particular night there was hardly any time to see anything, because we got maybe just 15 minutes of clear sky. The clouds briefly moved out, and then moved back in with a vengeance. The observatory offered people to refund their tickets or to exchange them for later dates; we didn't try to get either, especially since we were not coming here on a later date. So around 10 pm we left and set out on the 2-hour-long drive back to the ranch where we stayed.
Some of the practical things to know before going is that while there is a cafe at the visitor center, the food there is as subpar as you would expect from the only eating establishment in the 20 mile radius. For the same reason it also gets really busy. There is not enough place in the cafe to sit, and there are tables outside, but on a early March evening it was too cold to sit outside -- yes, even in Texas. (Not to mention that this part of Texas has desert climate, and the observatory is high in the mountains. People at the star party were bundled in triple layers and wearing blankets.) So, any sandwiches you bring from home might still be a better meal than what you get at the cafe. And in between the presentations and the star party there is no time to drive to the nearest town (Fort Davis) to eat.
Though the cafe area is very crowded, there is a small "oasis" in the visitor center: namely, a room that doubles as a space museum and children's playground. There is some (albeit minimal) plastic "spacey" stuff for kids to climb on, and a long, curved bench for parents to sit on. And, of course, there are interactive space-related exhibits, which can also occupy kids for hours.