In general you do not.
As you travel in Wayanad in a hired vehicle the driver doubles up as a guide.
If you and your family are travelling in your own vehicle, you will have a copy of the custom made itinerary sent to you by Prabha. You won’t need much more info.
However when you go to Edakkal caves and you are keen to know more about the location, there are guides employed by the Archeological Survey of India whom you could listen to.
If you are trekking or going out camping then you need to. There are excellent guides available depending on your Language preferred.