I live in Gettysburg and Lancaster is about 2 hours away with heavy to moderate traffic. When going to Lancaster from Gettysburg I would reccomend HWY 15 to the Turnpike. You could also take RTE 30 but it is very slow going.
Gettysburg Campgrounds in order of my preference would be Gettysburg KOA, Gettysburg Campground, Drummer Boy and Granite Hill. Drummer Boy is located near Hwy 15 and can be a bit noisy from road traffic. These campgrounds offer activities for families and children and also have playgrounds
Campgrounds near Lancaster: Hershey Highmeadow is at least an hour from Gettysburg maybe closer to an hour and 15 minutes but an ok choice. Adventure Bound near Lancaster seems very nice. Hershey/Elizabethtown KOA is also another I have heard is nice.
I use Trip Advisor and RV Park reviews online and that will help you with some reviews as well. Also campingpa.com is a great website and forum for campers in PA or campers wanting to camp in PA. My forum name on campingpa is "familycamper".
If and when you come to Gettysburg let me know and I could give you some information on things to do and see while you are here.