I retrieved this from the YBW site from a sailor who did this trip this year. Sorry his direct email
address was not present to also pass onward:-
"We travelled through the french canals last year to the med
and for 2 weeks travelled with a sailing yacht with 1.8 m keel
.they had a sign up saying 1.8m keel
on the front of the boat.
often they found it difficult to moor close to the bank because of the shallow depth
so the moored along side us .on 2-3 occasions they stopped dead in the middle of the channell and we gave them a tow off the mud and they said they could feel the boat dragging a bit on the odd occasion.
Once we hit the Rhone they had no problem I would say the most tricky bit was through the canal du loing,the canal du braire,the canal du centre
If you do get stuck there will be another boat along soon enough to get a tow from
We went through in August and hardly saw any commercial
traffic on the canals mostly on the big rivers which are pretty wide and deep."
Another visitor to the YBW site suggested routing east from Paris to the Canal D'est - saying that was used by small freighters drawing 2 M draft - and accordingly mininimising the chance of hitting the bottom.
Hope all this helps and if it were me and wife and Biscay in December - think you're looking to make the right decision.....