My older two kids have always loved the Rainforest Cafe, from a very early age. My second youngest, however, is absolutely terrified. We've been dining out with our children for the past 8 years, and it was at TRC, recently, that we had our absolute worse dining experience. Ds is 2, and he cried hysterically from the minute we walked into the restaurant until we walked out. There was nothing we could do to calm him down. We weren't even right next to any of the animals. He just cried and cried. I was glad the restaurant was pretty loud, so I don't think he truly bothered anyone. We did take turns taking him out at times.
So, it really depends on the child. My older two have always adored the place, as do all the other kids we know, who have been there.
Your kids will be old enough to talk through all of this first. Tell them about the restaurant. Explain that none of the animals are real, and that there is a pretend thunderstorm, that only lasts a minute.
You could also observe their reactions when you first walk in. If they seem upset by any of the animals, you could ask to be seated away from the action. Both of the Rainforest Cafes by us have a nice rainbow/fountain section, that seems to be a little off to the side from the active animals. I just noticed this the last time we were there (when we left ds with his grandparents so the rest of the kids could go enjoy). So, I think we'll try that seating when we get brave enough to take ds with us, again.