Wawona is a little far from the Valley--about an hour. It's also close to the road and you get some road noise. It's more peaceful than any Yosemite Valley Campground and it's closer to the Giant Sequoias at Wawona Grove.
That said, there's nothing in the world compared to waking up in Yosemite Valley and seeing the deep granite walls, domes, and waterfalls all around you. Also the competition isn't as fierce in April as it is in Summer. Reserve the first day you can. Use the volunteer-run website
http://www.yosemitesites.com/ to find when campsites are available. I have Yosemite Campground maps here:
http://www.yosemite.ca.us/maps/campground_maps.html