With small children or babies a motorhome that is well insulated to prevent winter weather from causing an un-warm environment is a must....and RVs are difficult to heat in the winter months in cold climates unless they have been equipped for cold climates.
With small children laundry would be a concern and most motorhomes with W/D are 34' or more in length. A W/D would appear to be a necessity. Class A are made in short lengths and with slides that increase their living space. They also allow use of the cockpit area for living. If one lives according to the lifestyle they live in a house then the cost of living would be similar.
Health care for the family would be a serious consideration as unexpected medical care can be totally unaffordable.