Who to hire for help with dual citizenship for my children

Do not hire anyone.No need to pay for that.Get in touch with the nearest Les Amoureux aux ban public.They will help you free of charge.They help bi-national couples and families

Were your children born in the USA? Were you French when they were born? If so, you need to register their births through the French consulate that covers the region of their birth. That should be all that is required, unless or until they need their certificate of French nationality. They would need this cnf if they want to pass on their French citizenship to anyone else. My husband is 60, born in the states to a French parent, has his French ID card and passport, and we live in France - I have a Carte de séjour via marriage to him. We will apply for his cnf soon, so I can then become a French citizen via marriage.
But you can see that it doesn't take much to ensure your children's rights - contact the consulate and send them their birth certificates (and possibly your livret de famille - the consulate will tell you).
Worry about the cnf later. They *might* need it to go to a French university, for example. We talked to our consulate at the time about what was needed for what.

See your section here: https://en.m.wikipedia.org/wiki/French_nationality_law

Good luck,
Julie