During the summer months, we have camped in Yosemite Valley's Lower Pines a number of times over the past 10 years in our 39' Berkshire. This past summer was the latest. Those valley sites during the summer months are gone within the first 1-2 seconds the reservation window opens. If you are able, I would highly recommend staying in the valley if at all possible. The crowds during the day are horrible, but the park is emptied early evening and particularly after sunset. (Assuming the valley is what you are after.) Then, when you wake up, you are already inside Yomemite! Here is an option for you to think about since you didn't get a site.
Rent a class C and stay at Indian Flat RV Park. It's the closest RV park to Yosemite - reserve it now. The next morning, pack everything up early and drive into the valley and park in the Curry Village (Half Dome Village) parking lot. This is where the campground reservation office is - little office at the corner of the lot. Get there before 6:30-7:00am - there should be parking spaces available. It will take about 45 minutes to get to the parking lot. Get in line at the little campground reservation office, they open at 8:00am. Sometimes the line starts to form at 6:00am, but that's usually a person or two. When the rangers open the office, they come out and put your name on a list in order of where you are standing in line (noting if you are tent camping, RV, length, etc.) Once on the list, go do some of your day's adventure. Leave your RV parked and take the shuttle to your destinations - you will never find a parking spot for an RV during the day. Now, make sure you come back by 3:00PM. 3:00PM is when the rangers hand out the "no-show" sites to you folks that were standing in line at 8:00 in the morning. If you were first in line, you are first to pick the site you want. I would pick the site with the longest number of days available. Who cares what the site looks like, you are in the valley! Also, they won't let you pick a site that won't fit your RV. If you want to be in the valley for 7 days (the max,) and they only have a 3 day site, then do this process again after 3 days. The two times I did this there were 12 no-show sites available and then 16 no-show sites the next time. Both times were the end of June.
Also, I prefer camping in the valley Monday - Thursday. The weekend crowds are unbearable - weekday is bad enough.
If you do get a site in the valley for your time period and if you want, go ahead and cancel your reservation at Indian Flat. They may keep a day's camp site cost, but being in the valley is way worth it!!