I think it depends on how long you plan to go for tbh.
If you are only planning 1 year then for your children in French school the negatives will outweigh the positives.
My dd was 6 when we moved to France, like pp have said fluency is an subjective concept and to be truly fluent takes years and a lot of hard work. She is 12 now and in some regards fluent in French, she went straight into the French system and is extremely comfortable in French but it has been a hard slog for her. Her French soon outstripped mine and she needed a tutor (every 7 year olds dream to do a full day at school then come home and start again
).
For the first year she barely spoke at school. French schools are different to English, they sit at their desk and follow instructions. Lunch is not part of the school day so your child either comes home or you pay for periscolaire (wrap around). Dd came home in her first year but her French suffered as 2 x 15 minutes play time a day at school was not enough to get her French going. 2nd year we payed for periscolaire and she improved much more.
French grammar is complex and she still makes mistakes, normal but other kids with French parents get this corrected at home dd doesn't and so it's noticed at school. Her vocab is not as wide as that of a native either.
That said, we dont regret anything, she is doing extremely well and she is very happy. We have had a wonderful adventure and the good far outweighs the bad. But if we had only come for 1 year dd would have had a very difficult year with no long term benefit.
As for the other stuff, yes it can be tough dealing with stuff in France if your language skills are not great but I have found most people to be extremely patient and helpful (Orange, health system and edf even have English speaking helplines) We have a double tax agreement so although you will need to do 2 tax returns you don't pay tax twice. French taxes are all online, you will need a French speaker to guide you the first time but after that it's much easier.
As for the pp who says that English forums are full of people stuck and can't move back, I cannot comment on that forum but mine is full of Brits terrified they will be forced to move back thanks to Brexit and looking to get French citizenship.
We have found french life much more laid back, family orientated and welcoming (my village even has a little festival each year where we celebrate our multicultural community). Good luck with whatever you decide op.