One day charter
? The time you have to be back at the marina will be a big consideration. Also, what are your preferences? Sounds like a quiet spot away from the city to anchor
You might think about Egmont Key. Not too far and the island is only accessible by boat. Nice beaches to walk around and large enough you should be able to find a reasonably quiet lee for anchoring
. There is no harbor as such so any big boats nearby can rock you with the wakes.
Your final choice will depend on the wind
. Be flexible in your plans. If you have to have the boat back by 5-6 I wouldn't go more than 10-15 miles away maximum.