Germany’s Romantic Road for kids (5 and 7)?

I’m considering taking my (then) 5 and 7 year old girls to Germany next summer to do the Romantic Road. We are west coast US-based, and they are proving decent travelers so far (we have done 1 international trip, a decent number of local or out of state flights, and about a billion camping trips). Husband and I have done Switzerland, Norway, Denmark, France, Spain, and Italy between the two of us, but not Germany. I thought a trip full of beautiful castles and small towns, as a little girl (interested in all the princess lore, as many are), sounds pretty amazing. We do not have any older, fairytale architecture anywhere near us (except the faux stuff at Disney!). But, I’m having a hard time finding any one’s experience taking their kids on the romantic road. This would obviously not be a romantic trip, but a family one. We would plan to rent a car and go at a moderate pace. I would avoid long tours inside the bigger castles, to be in tune with the kids’ tolerances.

Has anyone done the Romantic Road with their kids? Did they enjoy it? Anything to totally avoid or to ensure we don’t miss?