If you are leaving SC mid April don't be in too much of a hurry headed north. We have done it 3 times departing MD mid April the first time & running smack into a late season snow storm in N MN with very few CGs yet to be open.
In 2014 we were W of Calgary in the first week or so of May. Mud season with snow still on the ground in just opened CGs. The good news is that the critters are out & the snow still on the mountains is spectacular. Be prepared for some chilly nights. We spent the better part of a month going through Canada crossing the Yukon first week of June.
2018 is planned to be trip #4 north. We are in the very early planning stages. One big lesson learned in the first trip is to plan to change plans. Stay loose & go with the flow. Weather & mechanical things will happen. Always have a plan B & C.