Just thought I would add this regarding your point about having to go around Paris. The 2 hours you think you're saving likely won't be anywhere near that once you hit the traffic.
I drove down to Carcassone a few years ago and on the way down went around the Péripherique. It was gridlock and chaos. The middle of the day, baking hot, just awful.
On the way home, I decided to cut across to Poitiers from Limoges and take the A28 to Abbeville. Worked out to be similar timewise, maybe slightly longer, but was a much more pleasant journey.
Also to add what others are saying about the speed cameras. In my experience, fines are no longer finding their way through to the UK from EU countries, much like they never used to come through from France untill I think 2016. I've heard it's because since Brexit they no longer have access to the DVLA database so can't send fines to the UK. My evidence for this is purely anecdotal of course, but we used to get flashed regularly by the 90km camera just outside of Calais, and haven't had a single fine come through this year. We've also been flashed multiple times in Germany and Austria and have had nothing come through. The camera vans will still get you though, as they normally have a car waiting up to the road to pull you in and give you an on the spot fine.
To be honest though, the motorway speed is roughly 80mph in clear weather, so there's no need to go faster, just be aware of places where the speed drops to 110km or 90km, as cameras tend to be placed just after the speed change. Everyone I know uses a camera warning on their sat-navs. Technically you aren't supposed to, and the radar warning boxes are definitely illegal, but how will they tell your sat-nav has the warning unless they pull you over? I'd say they would be unlikely to pull a woman driving with 2 children in a car full of holiday luggage unless you did something to give them cause to.