"Dependent children under the age of 18 do NOT need a residence permit. However, an underage child travel document (‘document de circulation pour étranger mineur’ – DCEM) must be obtained at your local Préfecture after your arrival in France."
In my prefecture we have been trying to get a DCEM for each child for 1 year. The prefecture is not doing them at all, and they do not know when they will again. And the prefecture says the children cannot re-enter France without them. Our immigration lawyer says "as a practical matter" border control will allow the kids back in if you fly into France (but maybe not another EU country).
The residency for kids is a pretty good deal, but you just may not actually be able to get it (maybe in another year?).
But I actually do really like France. I want to stay here awhile. I've done everything above board, legally, legitimately. The people are really great, not like the stereotypes. It's worth all the hassle I believe, but I think people need to be aware of the reality of the difficulty of the process that France is advertising in trying to attract foreign tech workers.