We have a T-Rex cafe here in the KC area and it is much better than Rainforest, in my opinion. We have always found Rainforest Cafe to be too expensive and we've never really liked the food. T-Rex food is about the same price but the food was really good on all of our visits, and we've been 3 times now. The main complaint most have here is the extra costs. They have a fossil dig area (think big sandbox with buried plastic bones) and computer games but you have to pay $3 to get in (for each person and adults must accompany children). Skipping that area is near impossible as there is ALWAYS about a 1 hour wait for a table.
Having said all that -it is worth seeing and if your kids like Dinos even better. Our kids love it and for the family of 4 we usually spend around $100 which includes food, play area stuff and a toy for each kiddo. It is a fun treat for the kids for sure and the decor/theming is better than Rainforest.