any discussion of RCIA in general does not apply to Eastern Orthodox, who need only make a profession of faith, after enough preparation to make them comfortable in doing so, to learn differences in liturgy, practices etc. The DRE who is approached by an EO family should take steps to make sure the pastor contacts the diocese so the bishop can determine which rite they will be received into (usually that corresponding to their “home”). The average DRE and many pastors don’t have this knowledge.
as far as children of adults who are entering the Church through RCIA, those over age 7 are considered adults for this purpose and would participate in RCIA as adapted for their age and baptismal status. Younger children are considered infants and will be baptized asap, or when parents are baptized, and proceed to other sacraments with suitable religious formation at the usual age in their diocese. A baptized child younger than 7 is considered to be “covered” by the parent’s profession of faith, and is considered Catholic from the time the parent is received, The notation on the parish records should note his reception into full communion at this time. He then proceeds to the other sacraments at the usual age. this is in response to OP, not the other side issues. RCIA is not for baptized Catholics, although these candidates may join the non-Catholics for their catechetical sessions, but do not take part in the rites specific to RCIA, and celebrate sacraments at the time designated by the bishop for Catholics.
as a practical matter, when the RCIA is applied as written, when an entire family enters the Church, it may be that different members are “handled” differently, due to age, baptismal status etc., and the reasons for these differences must be explained carefully, accurately, several times over the course of preparation, to the parents and children.
the website for the AD of San Antonio has a good link to how to become Catholic, and to rules for pastors in administering RCIA, which covers precisely such topics as those raised here, and is a good guide for how it should be done.