We have never used Viator, I must say being able to get transferred from Airport to our hotel and as well our return to Airport.....and being able to book tours through your company is a Great Idea!
Kenya was our driver both times and she was very friendly and joined in our conversation....this made our trip all the more better.
***There were 10 adults and the van sent was a little small especially with luggage would have like a little more room since one person had to kneel by the door the whole distance.