I wouldn't worry and cancel as of yet. Sites are hard to come by and you're one of the lucky few. I try and camp in the Valley campgrounds at least once/twice a year and there have been plenty of sites saying I can't get in but I do (you can see my signature below). Yes, some I wouldn't attempt because of trees blocking. But first I would suggest going to Yosemitecampsites.com and Campsitephotos.com to check out the site you have booked and see if that helps. I also have an old printout that describes the site as 36x10 clear - partial shade, next to restroom, T or RV. Clear means there is nothing obstructing behind but it doesn't say how large a trailer. Your trailer will definitely fit you just don't know if there is anything obstructing you from getting in. If you want to hold onto the site for awhile I am going up mid May and can checkout the site for you and take some pics. You can also PM me so we can discuss it.
Cindy
