How old are the children? Are they able to read i the car? Some people get car sick reading.
We did long journeys as a child, Yorkshire to Cornwall, Lancashire to Spain, South of France or Italy.
Map books so we could trace our journey were used when we got older.
My mum would sometimes do us a parcel / envelope with a list of things on it so inside the envelope / parcel were toys, sweets, bits and pieces - all individually wrapped.
On the outside was a list of things
A purple car
A boat
First road sign for X
Eddie Stobart Truck
Ending with things near the destination so 'the sea' would be in the middle if we were going to France but at the end for Cornwall.
Every time we saw one of the things on the list we had to confirm with mum (sometimes she would hold on to the parcel) and then we could open one of the little parcels.
When we were young there were no child seats or seatbelts in the back of cars so my mum would make a 'bed' with suitcases in the footwell of the back seat, we would go to bed as normal, in the middle of the night we would be woken up, put in the car and go back to sleep.
Obviously I don't recommend the bed but starting in the early hours still in PJs encourages sleep.
Stop at the normal waking up time for breakfast and to change.