I just went on the tour on our Sept trip, and I loved it. However, I'm an adult who is really into science...esp. plants and how they grow. There was a LOT of interesting information.
I'm glad that I didn't take my girls (almost 7 and 4). I don't think they would have enjoyed it overall. There were fun PARTS for the kids (we got to taste some cucumbers grown in the greenhouses, feed the tilapia, release ladybugs at the end), but overall....our one hour tour turned into a 1.5 hour tour (we had a mister-know-it-all in the group who just WOULDN'T stop talking, and 4 people in electric wheelchairs, which took some extra time getting around). It would have been too much....especially the last part of the tour, which is in the main greenhouse and VERY hot! There weren't many places to sit, you weren't supposed to touch the plants, etc etc.
So, YES, I think the tour is totally worth the cost, but NO, after having done it, I wouldn't take kids that age unless they were super interested in the material. Only you know your children, though!!