We chose the half day tour as I was 24 weeks pregnant and didn't want to get overly tired, sunburned, or mosquito bitten. I was promised full mosquito gear in advance of the trip but didn't need it at all - heard/saw maybe 2 mosquitos the whole trip. Don was our guide and was a wealth of information and enthusiasm. Because he was so knowledgeable even the members of our small group who were somewhat fearful of alligators trusted him and enjoyed getting close to the alligators in their natural habitat. Most of the tour was a pleasant and easy kayak through the mangroves, and there were also two short walks, in a swampy cypress dome and on the Anhinga boardwalk. At the end I wished we were continuing on for the full day tour's saltwater kayaking, but I was also fairly tired by that point.
If you have a few days to explore the Everglades, you could take free ranger tours that cover all these areas, but there is no way to take all the free tours in one day. The Garl tour was pricy for our budget but worth it to us because we didn't have a lot of time, and because it really was a top notch tour. If we had just showed up at the park on our own for an afternoon we would have missed out on the feeling of really getting to know the Everglades.
The booking email tells you not to take a camera because it might get wet and that there will be a photographer taking pictures for you which you can then buy. There was nobody taking pictures of us - I don't know why they tell you that. Take a camera, and if you are worried about it getting wet put it in a dry bag for the kayak. We used a disposable underwater camera that I bought for snorkeling, but a camera around your neck should not get too wet. Tissue for pit stops is also handy, since the time away from restrooms is considerable. You can bring lots of stuff and leave it in the van while hiking and kayaking. Also, don't plan for the tour to actually end at 3pm as stated in the email. We started at 11am and ended after 5pm. That was fine for us as we didn't have anywhere to be, but let the guide know if you are on a tight schedule.