My family and I have hiked all of MD and agree with the other posters that it is one of the easiest sections of the trail for it’s length. Spring break will give you about 12 good hours of light and depending on your hiking style, you may find you wander a bit more than just MD (assuming you’re going all week). The lay of the land is relatively flat except for the climb out of Harper’s Ferry (up to Weverton Cliffs, a beautiful overlook of the town). As others have stated, you will pass through several viewpoints and at least a couple campgrounds (=flush toilets :).
As for parking, we have parked in Harpers Ferry (thumbs up to that as a terminus point - just check in with the Park Rangers and let them know your plans). On the north end, the official parking at Pen Mar is in front of a fence and only accommodates 3 or 4 cars. I have parked in the park for 3 days and still found our car safe and sound at the end. YMMV.
Any way you slice it, I think you’ll have a blast doing that section. If you want to try for a bit more, you can do the 6 miles south of Harpers Ferry which lops off West Virginia and continue down the trail to Bears Den Hostel. Don’t remember the mileage off the top of my head. Or you could continue north after Pen Mar and experience some of the legendary PA rocks.
Oh and I can’t resist mentioning that if the weather is right you might get a chance to see some Mountain Laurel or Rhododendron. MD is covered in it on the trail. Best of luck!
FarmerChef