My qualifications for my reply, Northern Delaware is my homeplace and I live in Myrtle Beach. I have driven back and forth many times.
My first recommendation is avoid I-95. For a more enjoyable passage take the morning Cape May-Lewes Ferry. Get to route 13 south, there are several ways, don't know when you are going, if summer it may be best to avoid the beach towns. First overnight at the southern tip of the Virginia Peninsula, several campgrounds in the area. Day two take the Chesapeake Bay Bridge and Tunnel south to Norfolk, which will be the only big city you pass thru on this route. Follow freeway thru city to Highway 17. This is the same rt 17 that passes thru Myrtle Beach, it is a nice easy mostly four lane road with bypasses around all the old bottleneck towns. There is no white knuckle driving like on I-95. Many places to overnight between here and MB.
You didn't ask about RV park recommendations in MB, but the crowd has been offering their favorites. The Grand Strand is a big place and traffic can get hectic in the summer so I would suggest staying in one of the parks closest to your daughters wedding. If you can word that in another query with the name or address of the wedding place I can assure you will get many suggestions. I may even let you in on the best kept secret in MB.