I like Conch Repubic Divers but have also dove Silent World and Quienscence and had good experience. Conch's big boat is really big and stable which is nice for winter and spring diving. They are also located a little further south than other Key Largo area shops and hit some shallow reefs and a the deeper Conch Wall reef that other boats don't get to quite as often.
This is a decent place to stay:
Key Largo Hotels | Ocean Pointe Suites at Key Largo | Tavernier Florida Keys Oceanfront Resorts
This thread has some good information:
http://www.scubaboard.com/forums/florida-diving/435116-help-florida-keys.html#post6502886
This thread has information on non-diving stuff to do:
http://www.scubaboard.com/forums/florida-diving/429631-suggestions-non-diving-family-keys.html
There are many casual bars, taverns, restaurants in the Keys, so you won't be bored in the evening. One of my favorite places in Mile Marker 88 since you can sit outside and watch the sun set over the bay while eating dinner or enjoying a beverage.