When packing for a road trip with multiple stops along the way place individual, full outfits (underwear, socks, and a full set of clothing) into separate ziploc bags. Remove as much air as possible to save space and label with child’s name. Then place all outfits into one large (or one per person)garbage bags. Keep a bag of pyjamas separate. That way when you stop for a night you won’t have to unpack the whole car. Just grab one ziploc for each person and the pyjamas bag and go.
Packing like this also protects the clothing you haven’t used yet from the elements like water and dirt.