Fishing just doesn't get any better there. In fact I too with wife and kids are going to Marathon for 2 weeks in the end of June.
Try
www.bootkeyharbor.com they have a nice website with lots of info about the area. They also provides tips and GPS numbers galor for the keys - most are reefs that are SPA's and some are old shipwrecks that are not listed on charts.
Speaking of charts - try
maptech.com as well the have a nice viewer that uses noaa charts that you can download from their site. You can also use this program to manage gps numbers with your gps - if you buy the full version you can use a laptop as a charter. I wouldn't go that far though. You can put your own notes on the charts you see fit as well. You can print chart packets like the ones you buy in the store for an arm and a leg. I have a complete set of charts for the keys. Your wayppoints and notes will print on the charts as well. Best of all its all free...
Hmmmmmm - being I went this far - when you print your chart packets --- get some tompsons water sealer and spray them down with a water bottle and then let them dry ---- like magic you have waterproof charts - don't kid yourself they are not tear proof though....
Enjoy
john