That's a tough call, being a holiday weekend. This time of year, they only have a few of the loops open, and if you were getting there in the morning I'd say you have little to worry about. But on a Friday evening on a holiday weekend with no storm (predicted anyway) you might think about a "what'll I do, just in case?" contingency. If you have any way of heading in so you'll be there in the morning or early afternoon, it would be less chancy.
You can't rely on any info from the reservation site during this season; they're all first-come, first-served and they have no info, but instead it will just look like everything is full.
As for camping in the valley being something to avoid, if you're after a wilderness experience of course it's not the place. But I love camping there; easy access to all sorts of fine, uncrowded trails with world class scenery, instead of worrying about meals you can hop on the bus and head to the Lodge or elswhere for a hot, no-hassle meal. On those long dark cold evenings, instead of a smoky fire you can go to the lodge's evening presentation, which can be an Ansel Adams flick, or various presentations regarding the park, wildlife, history, etc.
If you have a bike, they're invaluable in the valley. The bus is nice, but bikes are better during daylight hours.
If you want the actual sunrise, it comes up somewhere south of Half Dome (viewed from most of the Valley) this time of year, so if you got up early enough and headed to tunnel view, it should be a nice vantage point. You can get some nice photos of the early sun from the Ahwahnee meadow and Stoneman meadow (across from Curry) and the forested areas in between. Also the trail that goes along behind the Ahwahnee, eventually to Mirror Lake gets some morning sun. If you're around Ahwahnee meadow on the Northside drive side, look up at upper Yosemite falls as the morning sun hits it for a rainbow
http://www.pbase.com/roberthouse/image/65127870Aside from possible full campgrounds due to the holiday weekend, at times the gargantuan motor homes invade the place (I'm a tent camper and plan to stay that way 8^);
http://www.pbase.com/roberthouse/image/16156156the only other downside to me is the campfire situation. Many folks associate camping with a fire that burns eternally, and the valley doesn't have the circulation for it. I personally wish they'd have a firepit somewhere, and not allow campfires at all, or just for a brief time in the evening, year around. Currently they limit it to evenings in summer, but in winter that's not the case, and the smoke is definitely in the unhealthy category at times.
Enjoy your trip! Hope you get your site and all goes smoothly.
Gary
Yosemite Photo Galleries: http://www.pbase.com/roberthouse/yo