If the child is not dry at night and you expect to be driving at a time when your child will be sleeping for a long period of time, then I would stop somewhere before “bedtime” to change into pygamas and put on whatever your child usually wears at night (nighttime pull-up or something). However, if your child is toilet trained and does not wet the bed regularly, then it is not normal to put them into diapers. You need to plan more time for toilet stops when travelling with kids. Get everyone to go to the bathroom at every stop to avoid unnecessary extra stops. Also keep toilet paper and plastic bags in the car in case you need to make an emergency stop at the side of the road somewhere where there aren’t any toilet facilities.
i Know i wouldnt be comfortable in a JUST IN CASE DIAPER but there are out houses gas stations and even TREES that u can stop at never put a diaper on older kids it will hunt them for the rest of their lives and will also be a secret that they will want to tell no one especially if their pottie tranned.