Greetings Fellow Pennsylvanian,
Although my wife and I now fly on all trips to Florida, we used to really enjoy driving. I could write a couple of books about my experiences rolling down I95. It's a different way to get to Disney, but it can be an educational experience.
Funny, your question leads into my two rules of running the East Coast gauntlet. Rule#1 is ignore the massive amounts of advertising that starts in Maryland and keep your kids, your wife, your car, and your belongings away from South of the Border.
Rule# 2, do NOT stop for a night in Daytona Beach.
That said, I can highly suggest Hilton Head (or some of the surrounding areas for a slightly less costly stay). It's a fantastic area, and it's less than a half hour off I95.
Slightly further, and a neat stop for a couple of days on the trip back, I can highly recommend Tybee Island Beach, GA. It's near Savannah, and a little closer to an hour off I95. But it offers something a lot different than basic "Jersey Shore." It's a big shrimping area, and seeing the shrimping boats come back from expeditions is pretty neat. They have an historic lighhouse, several nice parks, sand dunes and trails, and plenty of nice beaches for family activities.
We're childless and have found it to be an awsome "adult experience," meaning lots of history and scenary during the day, sufficient nightlife when the sun goes down. And we've gone with two other families with children, and they found it to be filled with things to keep young ones busy, from age 2 to age 15. And the dining is wonderful, especially if you're into seafood. I can highly recommend Hunters for fine dining, or if you like fresh seafood and have a sense of adventure, eat outside at The Crab Shack, and don't forget to have a slice of key lime pie.
Here's a web site on the location:
http://www.tybeeisland.com/
Hope it helps, have a great trip!
Pat