With 3 kids in car seats i'd think you'd want 3 row seating to be comfortable.
Chevy Traverse, GMC Acadia are right around 5,0000#.
Ford Flex is a little less.
Those are the only 3 row seating towable vehicles under 5000# I know of.
Mountain driving performance is all about weight. They more you weigh, the harder it will be to pull the grades. Just take your time becuase you will be slow. My towed goes with me wherever I go no matter how far or how high. It's our rescue boat in case something breaks on the motorhome.
2009 Georgetown 350TS (bunks)
400W solar, 440AH 6V GC2
2009 Ford Edge AWD Ltd towed
2011 Honda Fit Sport towed