We also drive down from NJ but, we are in Bergen County, about 6 miles from the GWB. We have driven down a few times and have found that leaving in the evening and driving straight through works best for us. Sorry, I can't comment on taking the ferry because we have never done that but, if you head over to the transportation board ( driving 2,000 miles round trip)thread I am sure someone on there has some info on that. On the transporation (2,000 miles round trip) thread there are some wonderful people with great advice because they have made the drive a bunch of times, their advice is usually right on the mark.
Anyway, here are some things we do when we drive (my kids are currently DD14 and DS9):
-we have a dual DVD player in the car so we take along some old favorites and a couple of brand new DVD's. we have headphone for these so not everyone has to hear if they don't want to.
-we pack a cooler with: juice boxes, small bottles of water, grapes, string cheese, sandwiches etc. (we pack the ice in large ziplock bags instead of just loose in the cooler so the stuff doesn't get soggy).
-we pack a snack bag with: small cereal boxes (individual size), cookies, goldfish crackers, granola bars, mini muffins, apples, m&m's, (mini bagels are great too).
*packing snacks and drinks really helps save money because purchasing this stuff on the road at the rest areas or gas stations etc. can get expensive.
-if you have a small child in a car seat with their feet dangling try putting the cooler or a small suitcase on the floor in front of them so they can rest their feet on it. it really makes a difference in their comfort level when their feet aren't dangling for hours and hours.
-we bring a ball and frisbee to toss around at the rest areas for a little bit, 10 or 15 minutes of running around will be a huge help.
-when the kids were little we would stop for lunch or dinner at a place that had an "indoor playground" so that after the kids ate they could play for about 30minutes and it was the best thing we ever did.
-"state line goodie bags" are an awesome surprise for the kids. Basically just get some small lunch bag size bags and put a couple inexpensive "treats" in, the dollare store is great for that. Stickers, small notebook and gels pens, toy cars, other small toys, mad libs book, snack size bags of m&m's, chocolate coins etc. Check out the dollare store or the dollar zone in target for some great ideas. Basically just make up a bag for each child for every state line you cross, when you are crossing the state line give them the bag(if they're awake). I wouldn't start it until a few hours in because thats when they get restless.
-bring a pen and small notebook for the license plate game.
-the game 20Q (small electronic hand held game, size of a tennis ball)is really fun for the kids. you can purchase it in Target, wal-mart or toys R us.
-MadLibs are great
-pack a box of small garbage bags (keep them out just in case), they are great for actual garbage and for emergency vomit bags. also pack a container of wipes for quick clean ups.
*like I said earlier, leaving in the evening (shortly after dinner) works best for us. I try to sleep as much as possible during the day we are leaving. DH starts off the drive and will drive until about midnight or so then I take over.
bring earplugs so that the other driver can actually sleep and be ready for their turn driving .
I make sure my i-pod is loaded with some upbeat tunes when I am driving during the night and everyone is sleeping. I only drive with one earbud in so I can hear emergency vehicles etc.
I keep a bottle of water and a small ziploc bag of grapes and a small ziploc of m&m's next to me when I drive just to snack on during the night.
*please remember if you get tired pull over and take a small nap at one of the rest areas. 1 or 2 hours can help tremendously.
-wear comfy clothes and shoes for the drive (my kids usually wear sweats and a t-shirt or shorts and a t-shirt. even when driving at night because they don't feel comfortable getting out of the car in pj's).
*have a safe trip (sorry this is so long, I just tried to remember everything I could from our drives and we are doing it again at the end of June

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P.S. when we have stopped over it was in Santee, SC (we take 95 all the way from Jersey to Florida) and it is approx 12 hours from here. We have stayed in the Country Inn & Suites.