The journey down.We live near Nottingham, we like to cross over to Peterborough, then Cambridge before heading down the M11 to the M25 and beyond to Dover. I prefer this route as a) I know it well and b) it's saved us from some pretty nasty jams on the M1 and M25 in the past. So long as you get past Barr Hill nice and early in the morning your only major hold-up will be the Thames river crossing. We can do the journey in 5 hours but this is on a clear day with no stops. For 'family' journeys allow at least 7 hours. Get petrol at a Dover supermarket then take your pre-booked ferry crossing to Calais.
From Calais follow the following route - Abbeyville - Rouen - Evereux - Dreux - Chartres. This is the limit of what we can do in a day, we pre-book a night in a family room in the Novotel. The biggest hold-up this side of the Channel is likely to be Rouen, avoid the central bridges if at all possible and be aware that after Evereux there is a shortage of toilet stops.
By the way while the service stations in France are often beautiful by comparison and the picnic/comfort stops plentiful we find motorway food (and ferry food) in France to be almost as bad as the UK i.e. in-edible, so we always take picnics. Where in follows my next tip, when you leave the Novotel in the morning head for one of the nearest supermarkets, get a breakfast, something to eat on route and fuel for your vehicle.
Now head down the N154 for Orleans, then the N20 for 'La Ferte-St Aubin' and Vierson. At Vierson get on the A20 and head for Chateauroux. When you get off the A20 is up to you, but if you can leave by J53 you will avoid the peage. All the driving this side of the Channel should only have cost you about 10 euro, as opposed to over 50 on the main motorways. It also avoids central Paris and all the delays that ensue from there. You are welcome.
And just for the record we DVD and MP3 player alternately on the journey. Its the only way we can survive. The girls can't cope otherwise and we can't handle that many repeats of 'Frozen'.
Eating and drinking.If you are eating out go for set meals at lunch time it is a lot cheaper than evening meals and more pleasant in my opinion. However my top tip for family evening meals is the Marche Producteur http://www.marches-producteurs.com/dordogne they are basically local farmers markets with a BBQ facility thrown in for free (though some of the smaller ones don't so watch out). The set up varies but the chips seem to be ready at about 8pm and the grills are normally hot by then too. It is an incredibly cheap way to eat out and it's good fun too. Our family has a lot of food allergies and we find our limited French invaluable in talking to the producers who will happily tell you exactly what is in their sausage/bread/ice cream etc. It's even possible to eat well as a vegetarian but always take a salad in your picnic hamper just in case and everyone should take something to drink.
I'm not going to recommend places to go or stay, the area is vast and the choice wide. If you have found this page you probably already know many of them, go, enjoy and have a glass or two for me while you are there.
The journey back.We pretty much reverse the route going home but stop in the Loire for a couple of nights to do a Chateau or two and the Garden Festival which is amazing http://www.domaine-chaumont.fr/en_festival_festival. Then it's back on up to Orleans following the reverse route home until we get to a B&B or hotel in the Somme area for the night and catching the ferry home.
One last piece of advice, have a stop for fuel long before Calais and once you approach the city do not leave your car, keep the doors, boot or hatch and windows locked and have every space in your vehicle covered or filled. There are some poor desperate people out there who will do anything to get to a better life in the UK. Don't let yourself fall victim to them 'hitching a lift' seen, or unseen in your car. Whether you know about them or not you will get fined and a criminal record. That said please don't feel this part of the journey is particularly dangerous, it's like a night out in Nottingham - know the risks and what to do to keep safe.
Have a lovely holiday!