Providing a whole list of kids is necessary, in case the immigrant needs to petition for them at any time sooner or later. Certain kinds of negative immigration history might affect eligibility for a green card (or indeed any type of admission to the U.S.), so see an attorney if, for instance, the immigrant overstayed a past visa or was placed in removing proceedings. Any names which are ignored will likely lead USCIS to disclaim later petitions of this kind.