Two adults in a 2-berth motorhome can comfortably drive 300-400 km a day, stop spontaneously, and free-camp in self-contained sites that most holiday parks can't match for setting. Two adults plus two children in a 4-berth are slower (200-250 km a day is realistic), need more daily structure (food, washing, playground stops), and benefit more from holiday parks with kitchens, kids' rooms and laundry. The same Christchurch-to-Queenstown corridor is a 5-night trip for a couple and a 7-8-night trip for a family.
Vehicle and layout differences
Couples — 2-berth, automatic, permanent rear bed, internal shower and toilet. The extra rental cost over a 4-berth dinette layout is small and the daily quality-of-life difference is large. Families — 4-berth or 6-berth with a permanent Luton (cab-over) bed, separate dinette, larger fresh-water tank, and ideally a separate shower from the toilet.
Daily rhythm
Couples typically drive 4-5 hours and stop at 2-3 short attractions. Families typically drive 2-3 hours, do one main stop, then settle in early. The same 14-day route — Christchurch to Queenstown via the West Coast — works for both, but a family's version has 11 driving days and 3 longer base stays where a couple's has 7 driving days and 7 single-night stops.
What to book in advance
Couples — only the vehicle and the Cook Strait ferry if applicable. Day-by-day, holiday parks usually have a spot if you book at lunchtime. Families — book holiday parks 1-2 weeks ahead for the busy stops (Queenstown, Rotorua, Franz Josef, Tekapo) especially in school holidays. The good family rooms and family campsites sell out first.