Why do you not ask your daughter to help you find an outfit?
My sister took the advice of her eldest on a similar occasion and looked very nice indeed in a trouser suit, that tactfully disguised her very thin legs and a tummy that not only was the reverse of thin, but according to my sister, stuck out (the rest of the family could not see that feature, but she could and it worried her.)
Unless the wedding is to be extremely formal dress-wise there is no reason at all why you should not wear a trouser suit, or even a pair of slacks with a contrasting top.
If it is to be so formal that it takes place in the late afternoon with the gentlemen in tails and white tie, then go for a full length kaftan style dress or something similar.
And as the wedding is taking place in France, you are not obliged to wear a hat.