How many grandchildren do you have and realistically how many will travelling with you at any one time. The Coachman c-class will most likely have the cab over bunk for 2 extra sleeping positions. Both units will the couch and dinette for sleeping as well.
Get the floor plan that works best for you, slides IN and OUT. Personally,after owning a c-class, I now would go with an A. More living space, seating choices when the cab seats are swivelled.
Driving, pros, cons, personal preference for each, I might take a day or 2 to get used to either. Both units are the same width, approximately the same height. According to the model number , the A is about 3 ft longer, not much when driving on the highway.
Ken