We've done T-Rex gluten free, it was really good. We only go every 2 years so I have to say that I'm not ringing up any specifics

and it's DH and DS1&2 who are celiac and I don't remember what they ate. But I do remember that the last time 10/2011 our chef was very personable and gave us a lot of time, and knew his stuff about g/f. The atmosphere is really pretty cool, too.

The theming is pretty great, there is at least one hidden mickey in there that I can remember, and of course my boys LOVE the Build-A-Dino.
We also do Rainforest each time we go, albeit the one at AK, but I'm sure the menu is the same. The one thing I recall from there is that the dessert choice is limited. However, Ghirardelli ice cream shop is right there! And they have a ton of g/f there. They keep a binder at the registers, so go up to the register and ask to see it while you wait in line to order.
I choose T-Rex at DTD because we hit Rainforest on our AK Day, it's harder to pick just one

but I think I would pick T-Rex. I think the menu is a little better, and the atmosphere is cool. Also, there is a Rainforest not far from home if we every really craved the jungle, but no T-Rex anywhere near us. That may factor in for you, too.
DH and I have also had a couple of "dates" at the Wolfgang Puck place (both the quick part downstairs and the upstairs restaurant) and he's had great g/f meals there. They're really knowledgable about GF there too, even when DS was the first one diagnosed celiac in 2007 our server knew about g/f and how the chef could accommodate (way back before it was hip LOL).