My wife and I just got back from Key West a week ago. I would recommend you stop by The Angling Company http://theanglingcompany.com/. They can hook you up with what flys you'll need and tell you where to fish. What impressed me about them is that knowing this was my first time in the Keys and first time fly fishing in saltwater, they did not insist that I needed to book a trip in order to catch fish. In fact, the subject never came up. But they do 1/2/ and full day trips for both fly fishing and light tackle. So you and your dad should be all set. As far as buying a license, they do not sell them in fly shops. I had contacted another shop there is Key West before our trip, but they never replied back to me so I blew them off. As far as buying a license you an go to myflorida.com. They do not sell them in the shops.
I took an 8 wt with me and at times wish I had a 9wt. There were some days the wind blew pretty hard to the point that having a 7' spinning rod along would have been a plus. I know both St Croix (Feathercraft sells them) and Orvis make 3 pc travel spinning rods for fishing in saltwater. Ken at The Angling Company said he though having a 7' spinning rod is good insurance for the days the wind blows you off from fly fishing. The line I used was a floating coldwater Clouser. Since the temps were cooler while we were there, I was able to get away with not using a line made for hotter tropical weather. I plan on buying one before we go back next year.
We did not do allot of "tourist" type things while we were there. But we did take the Conch Tour Train and enjoyed it very much. Learned allot about Key West and it's history that we would have not learned about otherwise. And we ate lunch one afternoon at Sloppy Joe's bar which was Hemmingway's hang out. There are some gorgeous sunsets there and Mallory Square is a local gathering point for viewing and there are a couple of piers down by the beach from where you can watch the sun set.
Good luck and I know you'll have a good time.
" If a man is truly blessed, he returns home from fishing to the best catch of his life." Christopher Armour