The Shamrock Farms tour is appropriate for all ages. It is not especially strenuous. The ability to step in and out of the tram, and walk a flight of stairs (with a handrail) will be your only requirements. There is an elevator for those that can't use the stairs.
Having taken the tour, I believe that the people who'll get the most out of the tour are ages 8 and up. It isn't that there aren't things to do for the little ones--there's actually a ten minute stop at a special and very enjoyable playground. Still, this is more an educational tour than a tour where kids run around and play, as might be offered by some smaller farms.
Roxie told me this, and said I can tell you: The cleanliness of this facility is striking. You'd think that with 10,000 cows, that there would be overwhelming odor. Not true. When you take the tour, ask them why.