I'd probably lean towards the keys. Miami is decent sailing, with some protected water, and yes, if your weather window is good,
Bahamas are 'across the street' - but that time of year, we're starting to see some early fronts, so I wouldn't necessarily bet on a perfectly timed weather window to match your
vacation.
Tampa Bay area is fine sailing actually, and I believe the W. Coast of FL is a wonderful place for a charter. I may be a little biased, or just know most of the places to go I suppose, but the best part is that our 'inside' is really inside. If it gets snotty, you can still travel. The
depth issue is not a problem save for a few passes and yes, the
ICW isn't all that wide in places, so depending on wind direction, not always 'sail-able' inside - however, Tampa Bay is great,
Sarasota Bay is great,
Charlotte Harbor is great, Pine Island Sound is great... and all of these have fun and unique destinations along the way, and protected water, marinas/services and
anchorages close by if needed. Water in our area is nothing like up in Miss. Sound or around that portion. Much prettier in my experience. Rarely brown like that, unless we get a lot of rain. That time of year it will be nice and pretty clear.
As for the Keys, Key West is...well, Key West. and all that comes with it. The water down there is very nice / clear (provided it's not stirred up from one of those aforementioned fronts) and there is no shortage of destinations there either.
Head W. to the Tortugas, or East (North) up the island chain and you'll find plenty to do and see. Sailing 'inside' down there means inside Hawk Channel which is fairly well protected by the reef and entirely functional in even a bit of a blow. The main reason I would suggest it is because mainly with the geography of the keys - you feel like you 'went somewhere'. it's just a unique place in general compared to Miami or W. Coast FL... so for a
vacation, I for one, like to feel just like that - like I 'went somewhere'
Have fun, and if you have any specific questions, feel free to ask. I've travelled all of the above areas many, many times over.
Rob