Errm
Sorry I have been away or I would have replied to this earlier; you will need a heavier approach than you would use in the UK the tackle you describe is fine....... for catching bait. I normally use a 9 foot 50-100g spinning rod and an 8weight fly outfit for the bonefish and a 30-50lb class boat outfit with a 4/0 class lever drag reel for trolling. I also use the spinning rod for live baiting etc. for line I use either 30lb braid on a 60 class spinning reel (I use an Okuma Cedros), and a have a spare spool of 35lb mono as it has more abrasion resistance if fishing over coral reefs. You will need to use a trace I use 60lb wire but use 150lb when trolling fro the likes of Wahoo King Mackerel etc. I use 100-20lb mono for Sailfish, Dorado etc. and I would use a rubbing trace of 100lb mono if you go for the big Tarpon.
There is no tackle to be had on the Cayos so you must take your own so take a good selection of poppers, lures, hooks (I like using octopus patterns in sizes from 1- 10/0 but small patters (sizes 8-2), are useful for baitfish and sets of sabikis and hokkais work for this as well.
as for the fishing the beaches on Cayo Guillermo are extensive coral flats and are very shallow and completely exposed at low water they are good for bones and odd needle fish and Ballyhoo but little else the Causeway bridge on to the Island is good but always full of locals, the rocks at Playa Pilar are also good in the evening but the big Tarpon that used to be there between May and September are few and far between. The lagoons around the hotels have baby poons in them and are fun on spinning gear but are under a lot of angling pressure.
Charter boats are available at around 450 CuC's a day (cheaper for half days and standby’s). You can negotiate a half day mangrove or inner reef trio for around 150CuC's per day and guides are 180CuC's a day but they will take you off island to the excellent marks around Cayo Paradon Grande.
Tony