IMHO, Both T-Rex and RFC are equal and very similar, however I'd have to say T-Rex is a bit louder and scarier. Having eaten at TRex, our experience was that the food was bad. DS's ribs were filled with shredded bones, DD's salad had a 'funny flavor' and made her sick. Meinwhile, the food at RFC, after eating there more than 5 times has never been bad.
OP, you asked which was better for kids: The AK RFC is the best of the three however, but it sounds like you want to be in DTD, for that I vote you visit the shops of both and hit Mc Ds for food that will please your little one.