Nightly rates can differ for each, and some campsites offer family rates.
Most campsites charge a different nightly rate for adults, children and infants, which is why the booking page asks who's coming. Infants often stay free, but that's up to each campsite.
Some campsites offer a family rate: a set price that covers a typical family, with a per-person charge if your group is larger. If a family rate applies to your booking it will show in the price breakdown.
Email support@pillowcase.io with your campsite name or booking reference and we'll pick it up from there.