Key West has a beach or two but if you are driving I would say my favorite place in the lower Keys is Bahia Honda State Park. They have a nice beach there...very tropical and undeveloped. If you guys have any boating experience what so ever, then renting a boat and heading to Looe Key is the way to go. There are boat rental places on Big Pine Key which is the closest key to Looe Key which is actually a big coral reef complex. Snorkel head boats are nice but renting a boat and spending the day on the water is awesome. You got to try the deep fried Key Lime Pie at the BBQ place on the Gulf side of US 1 right before the 7 mile Bridge near Marathon.
Bob, Tonya and the kids
11 Rockwood Roo 233S
08 Grady White Seafarer 228
08 Tundra 5.7 liter 4x4 crew cab TRD limited
08 Toyota limited 4 Runner Iforce V8 full time 4WD, tow package