Your hubby is on the right track, but he still may not have room for his espresso machine.

Even a huge 5W is no more than 400 sq ft and galley space, bathroom, etc. is going to be limited in the largest of them! Kids need space too, and on rainy days or longer winter nights it will seem like you have none. Cabin fever time!
I think you need to be looking at 35-40 ft models. Yes, you will have some campsite limitations, but you aren't going to be camping in secluded lakeside spots (no matter what those lovely RVIA ads show). There are plenty of campgrounds with large enough sites and adequate campground guide info to locate them. We drove a 40 ft coach for 12 years and never had to struggle to find a place, even in New England where campgrounds are often older and smaller. Some were a bit snug, but always adequate.