Earlier this year I did a 5 day bareboat charter
on a Hunter
41 out of Key Largo
and the upcoming October issue of www.southwindsmagazine.com
will feature the article I authored on that trip.
Another couple options are www.sailfloridakeys.com
There are a few other small Keys companies you can find on a Google
search and most companies in Miami
and Ft Lauderdale suggest a Keys itinerary.
The Keys are a great charter area with lots to offer, although with quite a bit of shallow water
that will challenge your nav skills. Based on your described experience level - I would caution that taking a large group on a large boat for your first bareboat charter might not be wise.
Feel free to PM me for an offline detailed discussion - chartering is such a great way to go as long as the trip matches your capabilities.
Best to you!