If you boondock 30% of the time I would stick to the el/propane refer forget the solar for now and get 2 6v GC batteries. You will have more than enough power for 3-5 days dry camping if you just camp in the NP's. If you have don't have to watch TV our play video games or use electric devices while dry camping. As a data point I dry camp only and in 7 days my 2 Sams club batteries are down to 50% SOC without solar or genset usage. The limiting factor is water in 7 days my 60 gal tank is almost empty and it is time to do laundry. How much water is in your trailer? With kids you will probably run out of water before battery power. The other thing to consider is the size of your gray tank, even if you can carry water from a GC faucet, US NP's don't allow you to drain gray water at your camp site I doubt Canadian NP's do either.
