kini Kini tours is a great tour company (at least my experience with them was good - see my other posts about the company/my experience with the company). I should also point out that I would not recommend having two riders on an ATV on the way to the Natural Pool as the rough terrain makes it easy to get off balance and flip the ATV. Additionally, if your wife is a little apprehensive about taking an ATV tour, I would definitely take a jeep tour (trust me - I have been in your shoes before). The Natural Pool is a definite must see!

Half day vs. Full day tour - it depends on what you want to see/how much time you want to devote to the tour. I have done both types of tours and both were great.

Snorkeling - I would suggest going to Baby Beach for snorkeling. Some tours offer a stop at Baby Beach and give you equipment to use while you are there (you can stand in the narrows and watch fish there). You may also want to investigate a tour that includes a trip to DePalm island.