In the 21st century, most of the people I know have one or two kids but in the 1950's Mom and Dad might have been a little formal on the outside, but behind closed doors they were all about repopulating the planet! Most of the families I grew up with in the 1960's had 4 kids. Catholics were immediately recognized for having 6-10 kids! Modern requirements for seat belts and kid seats make a minivan a necessity for any couple with a love of those little rascals, but back in the day you could get away with a nice 2-door wagon.
You couldn't tie them to the roof Romney-style, but with a full sized wagon you could easily get one or two of the small ones up front between Mom and Dad and 3-5 in the back seat depending upon how big they were. On long trips, you just stacked 'em like cord-wood in the cargo area.
Powering this thing is a "great running" Chevy 454 cubic inch V8 mated to an automatic transmission and a Ford 9-inch rear end. Side-post battery (with composite anti-sparker) held in place with a bungee cord was not standard equipment in 1957.
See another 2-door family hauler for less? firstname.lastname@example.org