Have been to Hershey area many times, but not with our RV. Have looked around Hershey Highmeadow CG to check suitability for our RV, but remain uncertain. The points about the RR are on-target. It is very busy and noisy. After a full day of amusement park, I would like un-interrupted sleep. The up-side is that since Hershey owns it, they provide free transport via bus to Hershey Park. That saves $ and the hassle of a long walk (usually) from parking to park entrance.
One place that I did not see mentioned that would be great for kids, is a very large teddy-bear place near Gettysburg. I'm sorry that I don't remember the name, but you will likely find ads for it near central PA. It's about 45 min to an hour south of Harrisburg.
There is a nice, small community about 5 min East of Highmeadow CG, called Hummelstown. There is a nice pharmacy/gift shop with all sorts of trinkets, a very nice toy store in town, and a great diner that offers decent meals at a good price. The down side is that there is not much room to park an RV.
Best wishes for a safe trip to PA.
Bob