I am likely in the minority, but I thought T Rex was chaotic, touristy, and served mediocre food.
I started taking my kids to Raglan Road -- right next to T-Rex -- when they were 3 and 5, and they insist we go there twice on every trip (they are now 7 and 9). The live dancing and music keeps my kids slapping the table for hours each trip.
T-Rex isn't even on our radar anymore. It's in our bottom 10 Disney Restaurants. If you want to see it just walk in and look around for 2 minutes.
So I'd recommend you consider RR over TR. I don't know anything about your tastes, but IMO, RR is far superior.