The Wawona Hotel Dining Room was a wonderful gluten-free experience for my son during our visit. We enjoyed a large portion (probably 50% was gluten free) of what they prepare for their Sunday Brunch buffet. We were also told that they have gluten-free items on their dinner menu but were unable to come back that day - unfortunately we discovered this on our last day at the park.
For the most part, we cooked for ourselves in the kitchen at the house we stayed in during our trip. Since half of our food got left behind at home (long story), we were fortunate that the market in Yosemite Valley had adequate choices to make gluten free meals at home. However, other than the Ahwahnee Dining Room which is expensive and more formal, we did not find any other gluten-free options at restaurants in the Yosemite Valley.
For our final day, we decided to look around for Sunday brunch options. When I called the Wawona, they were very friendly and helpful. They assured me that they are experienced in providing gluten-free options (as well as many other options for other dietary restrictions) at their dining room.... and even told me they would show us which items in their buffet were gluten free... so we decided to go.
When we arrived, I made sure to tell them we had called about the gluten free items. I was pleasantly surprised when it was the chef himself who then came out to greet us. He personally walked my son and me through the buffet showing us which items were gluten-free.
Near the end of the meal, I asked the waitress about dessert since there were no gluten-free options on the brunch. She happily gave me two options for dessert (we chose tapioca pudding)... when she brought out a heaping sundae dish of tapioca pudding, my son's eyes popped right out of his head in surprise!
After the meal, we ended up meeting one of the kitchen staff members. She let us know that she herself has been eating gluten-free for 30 years... now it all makes sense that they understand so much about preparing gluten-free food there!
I highly recommend this based on our experience.