So we decided to take the trip, with just a few days to get ready. I checked on the web and found that Yosemite's campgrounds are opened for reservations exactly five months ahead of time, and are all gone within the first few hours. But as luck would have it, there was one cancellation for a spot in the Valley the day after we were planning on leaving, and I immediately grabbed it. So we packed up and drove all day Sunday, got to just past Sacramento, and headed to Yosemite the next day. We had our first night, but the campgrounds were fully booked for the next two days; but there's a catch: if you arrive at the reservation booth very early each day and put your name on a list, and come back at 3:00 that afternoon, and there have been cancellations for the next day, they'll hand them out per the list. There were usually 5 to 10 available, so we managed to get a spot each day.