Welcome to the forum! Not much privacy or separation in an RV. Sometimes there is a rear bedroom with a thin door between areas in a larger Class A RV. The front compartment would then have to accommodate one couple and the kids.
Is it doable, yes but a larger Class A will restrict where you can park it when sightseeing as I assume you will not have a rental car to drive as well. You may be better off to consider one small Class C rental RV for each couple. Easier to find parking when at sightseeing places where you need to get out to enjoy.
Expensive ...... yes.
RVing is a wonderful experience and if you can adjust to being very close in a small place when not outside, you could have a great trip. EL Monte RV and Cruise America, as stated above, are the biggest networks of rentals.
Did not see where you intend to go nor what time of year. Weather can adversely effect travel so be sure to add that to your planning phase. Extreme heat or cold creates issues for RV travel as well as sightseeing. RV Air conditioners tend to be not so efficient in high heat areas! Summer time on the roads in America can be very busy and even getting reservations for your overnight stays may require some considerable advance planning and obtaining.
Best of luck for a grand adventure exploring our beautiful and diverse country!
