We have been there for trips (we usually go for a week at a time) and are actually looking at going back this summer again.
We stayed at the KOA Campground right in Gettysburg and it was amazing.If you're a camping family I highly recommend it. They have the cabins as well if you want to semi-rough it, although I would never say staying at a KOA was roughing it
This is ALWAYS where we stay too down there. You can truly do the camping thing. We usually rent a 2 room cabin. They have AC. However they even have deluxe cabins that bathrooms and kitchens too. It has a great location and it's on such pretty ground.
You have to do the battleground tour. This can be done by various tour buses or you can rent the tour and play it in your car while drive it yourself. This takes several hours, but it's truly amazing. If you stay at the KOA, they have the tour for your own vehicle right there for rent.
We also like the proximity of it to take day trips to Hershey and Lancaster.
If you like to shop there are great outlets in both Gettysburg and Lancaster is filled w/ them.
For the Ghost Tour we did the Mark Nesbitt one and really enjoyed it. It was not "scary" but the stories were very interesting. I've done a lot of these different ghost tours in many cities and mostly they usually are more about really great historic stories than ghosts. This particular one was way better than any I did in Savannah, and that is supposed to be even more haunted.
We usually go over summer. However, I would shy away from the 4th of July personally. I think it would be great to see the re-enactments. However, it is defintely going to be more crowded at all the attractions and more expensive too. Remember the Battle of Gettysburg was July 1-3 so that is very busy time there w/ events.
They also usually do a big motorcycle even there the second week of July.