We like to break our journey up every two to three hours or so. Driving through France is great as they tend to have designated areas spaced out about every 20km, alternating between service stations and rest stops. This makes it easier to plan stops especially when travelling with children.
The main difference between the service stations and rest stops is that the service stations have the restaurants and petrol stations, like in the UK (and can be expensive, like in the UK). Rest stops will have more basic facilities, like toilets (remember to have loo roll and hand sanitiser with you); picnic benches and sometimes a children’s play area. The signs on the motorway advise you of the service types available.