I have yet to find any one site or any app that will actually give you a route and all of the things that you are looking for specifically for an RV. And I say this because in an RV you have routing considerations that Streets and Trips, Delorme, Google Maps, and Garmin and all other car GPS units do not take into consideration and that is height, weight, and road restriction. There are a two GPS units made for RVs that will do this - and show campgrounds along the way- one by Magellan and one by Rand McNally. There are are a few GPS units that are made for truckers and these will work for an RV as well - one is from Garmin.
When planning a trip, I use a variety of resources and put them together. I check out the road restrictions in the states that I will be in through the state websites, check similar lists for low clearances, and then put them together with a route from one of the standard navigation sites. Free software called Tyre will do this nicely using Google maps - and the route can be transferred to a Garmin or Tom Tom GPS. Because in the Northeast there are a lot of areas with restrictions and low clearances, I make absolutely sure that the route on the GPS matches where I can take my RV and if it doesn't, more waypoints need to be added to route myself around those roads. Campground destinations are added from the site linked above.
The easiest solution is to get one of the RV GPS units - as it will do most of this for you.
I looked at the RV GPS units and I think based on my review of the units, that the Garmin DEZL 560LMT for truckers and rvs is the better unit. My main focus is using roads that my MH can travel without issues. Picking a campground is easy with my Good Sams book so I don't need a GPS to do that for me. Just one more thing to confuse you.
The other posts are right on ... you will need more then one way to get all the information need for a safe and simple route.