As another poster said the Hidden Passages may be too much. It's 186 steps down & same back up. During that tour they stress the importance of not touching any of the formations as they are very close. If you don't mind carrying a 4 yr old up 18 stories worth of stairs then sure. The Discovery tour still has a climb but it's more gradual. There was a 5/6 yr old girl on that tour with us & she did good but was tired by the end. Plenty of other activities to do as well.
I took my 18 month old and she enjoyed the maze, panning for rocks, the rope course, and of the snacks and drinks. As far as the actual caverns, the hidden passages tour is too slow for her she like to move alot. The discovery tour not a problem.
If he/she can walk on their own then it's not a problem. You may have to help carry them at times. I've seen parents struggling with little ones at times. A great alternative are the ropes courses, the little mazes up top and even more-so, toddlers love the wildlife park right next door! And you stay in your car. My three-year old niece loves it!
No. Not is good for a 4 year old.
We just took our 2.5 yr old. He loved it. Had to carry him out of the caverns though. They go pretty deep.
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