Great write-up by mgirardo. We go to Jeykll Island for weekend getaways, but we don't stay at the CG there. We stay at the Hampton which allows pets.
That being said, I have driven through the CG, and it isn't my cup of tea. No privacy between spots and rather crowded. It could be OK as a base of operations to do the things mentioned by mgirardo - we have done them as well.
They have an excellent bike path so bring bikes if your into that. There is only one or 2 places good to eat - some bistro - can't remember the name, and the Westin Hotel's restaurant - oh, and the Club Hotel. We hung out at the bar one evening.
The historic district also has a pottery shop where they sell pottery made in the basement. Lots of sand dollars and sharks teeth can be found on the beach. The sea turtle rescue is a must-see.
Have fun - and tell us what you thought of the CG.