okay then. First up I’m going to say I wouldn’t personally attempt this with a 1 yo.
There’s only so much CBeebies a small child can watch in my experience, and your passengers will go bonkers trying to keep the child entertained.
I’d accept tolls otherwise the journey will be gruesomely long.
And I’d cut out Rome - it’s just too far with a baby.
So here’s my plan:
Depending on your starting point you might make it to Reims on day1. That’s a common place to break and lots of budget hotels without needing to head into the city. Novotel Tinqueux is nice and has an outdoor pool, about £220 per night for 6 people. Or you could do the Ibis for £100 less. I wouldn’t plan to go too far on day1 in case of delays with the tunnel crossing.
On day2 I’d bomb it down towards Genoa aiming to stay there for several days. Good street food and market, old town, beaches nearby, proper Italy. It’s about 10 hours from Reims though, so a tough day for the little one. So maybe you find a second break between Reims and Genoa? Let’s assume you do that so you don’t get to Genoa until day3. Pick somewhere a bit random for night 2 - usually fun and low risk/cheap way to spend half a day in a town or area that tourists don’t really visit.
Stay in or near Genoa for nights 3 and 4 . On day 5, shortish Drive down to Pisa during baby’s long nap (probably mid afternoon). Stay in Pisa overnight
Day 6, Spend whole day in Pisa then head to Florence about 1.5 hours drive. Book an Airbnb and stay for several nights.
On day 10: Florence to Como , 5hr 30 stay overnight near lake como and add a second night so you can take in the sights.
Day 12 lake como to Colmar in France (totally beautiful and amazing food; like a mini Strasbourg). 5.5 hours drive so start in the morning Spend your afternoon and evening in Colmar!
Day 12 Next day drive back towards Calais (7.5hours) . We find we benefit from a final stop before heading back. We like stopping at a B&B in or near Dunkirk and make a pitstop at the beach but you could do Calais itself.