Hi fellow Marylander!
I've made the drive from Baltimore many times. It takes about 14 hours, depending on traffic and number of rest/gas/food stops.
There is really only one viable route from central Maryland to WDW - I-95. There are no mountain passes - I-95 runs parallel to the coast, so it doesn't go through any mountains. There are no tolls on I-95 south of the Fort McHenry Tunnel in south Baltimore (Toll $2). Terrain from Baltimore to WDW is mostly flat, boring, monotonous, empty interstate.
Take I-95 all the way through Virginia, the Carolinas, and Georgia. Once you cross into Florida, you still have about 3 hours to get to Orlando.
When you get to Daytona, you get off I-95 and onto I-4. At that point, you're about 1 hour from WDW.
I-4 goes directly past WDW. There are multiple exits from I-4 that lead into WDW property; which one you take depends on where you are staying.
I like to depart super early in the morning - around 4am. This puts me into Orlando around 6pm; early enough to get a nice dinner, relax, and unpack the vehicle without staying up late, and to get a good night's sleep before starting the parks the next morning. It also allows me to avoid all of the Baltimore and DC morning rush hours, and usually allows me to miss most of the Richmond rush hour, too.
Tips:
* Rush hour through DC is one of the worst on the east coast, except perhaps NYC or Boston. If you are driving on a weekday, plan your departure so that you either drive around I-495 (Capital Beltway) before 6am or after 7pm. On Friday, make that after 8pm.
* Change drivers about every 3 hours. If you have at least three drivers, that's only about 2 shifts each, making the whole trip much easier.
* As you approach Richmond, VA, get off onto I-295, the Richmond Bypass. It looks longer on the map, but the speed stays constant at 65mph and it's 3-4 lanes each way, making it much better than staying on I-95 and going straight through Richmond. I-95 through Richmond slows to 55mph, is much more crowded, and has a lot of twists and turns.
* Take either a good map or a GPS unit with you in case you need to find a detour. GPS units are also good for finding gas and food stops.
* Don't let your gas tank dip below 1/4 full. You never know when you'll hit a long stretch with no gas stations.
* Take a cooler with a wide variety of snacks and beverages. Don't just get one type of snack or beverage; on a long drive, you don't want to be stuck with the same chips and soda the whole way.
* Put cleaning supplies - water, wetnaps, paper towels, etc - where you can get at them in the car, in case of spills and dirty hands from snacks. A trash bag to handle the refuse of the snacks, drinks, and cleanups is also a must.
* Other things to put in accessible locations like glove compartments or center console organizers - Sunglasses, contact lens solution/rewetting drops, daily meds, common OTC meds like ibuprofin Rollaids, and Imodium, dollar ponchos (in case you stop for gas in the pouring rain), towels (ditto), sunscreen (in case the sun is shining on the drivers arm for hours on end), flashlights (in case you need a potty break in the wee hours of the morning, or in case your kidlet drops his favorite happy Meal toy under the seat), pocket first-aid kit (you never know when someone might trip and skin a knee or elbow), and if you're stringent on oral hygiene, some of those new disposable toothbrushes.
* Do some preventative car maintenance the week before the trip - change the oil, have all of the fluids checked, check the brake pad thickness, check the air filter, put on new windshield wiper blades, apply rain-ex, check the tire pressure, and have the car washed (clean inside is more comfy for a long drive, clean outside makes it easier to see any fresh dings or scratches as you go)
* If you use fuel injector cleaner on your car, consider getting a couple of bottles and putting them in at each fuel stop on the way down. Continuous highway driving lets that stuff do a thorough job of cleaning the system, and you'll find your engine working better by the time you arrive.
* Keep your eyes on the national weather forecast in the week before the trip so you know what to expect. You may need jackets when you leave Maryland, but it will get warmer as you get farther south, and you might need rain gear on your stops or when you arrive.
* When you depart, have someone start the car about 10 minutes in advance to warm up the engine and get the heat or A/C up to speed for the rest of the passengers. Then, you can all dress comfortably for the car environment before you go and won't need to worry about pulling off jackets when the car warms up, or suffering extreme heat until the A/C cools it down.
* Seat-back organizers are great for back-seat passengers to use for iPods, DSs, sunglasses, paperbacks, etc.
* Pillows come in handy if you leave super early and want the kids to remain asleep.
* Whoever goes to bed earliest the night before can drive the first shift in the morning.
And remember - it's vacation! Don't stress over traffic, delays, or problems. Relax and take it all in stride. If you arrive late, so be it; you've got all night to rest up, and you can always sleep in the next day. It's vacation!
