We went with Seaduced last April and had a great time. Tevas worked fine for the short hike. We got those waterproof coleman bags from the camping section of Sports Authority and they worked like a charm. There is a large locker that you can lock your dry clothes / Towels and such in while tubing. Definitely take a towel with you. Breakfast was included, fruit and muffins and water/juice from what I recall. Lunch was also included at Jaguar Paw and very tasty. We had asked in advance for beer and rum punch on that trip (as they don't normally have those) which were handy on the bus and boat ride. The Zoo was real neat as that is part of the trip too and we had fun on the boatride back. You can e-mail SeaDuced directly for more info as well. If you also search this board for "cave tubing" you'll get a lot of good posts on the topic also.
Andrea in Atlanta