According to the C's the soul doesn't get fully seated in the body until later in life, sometimes as late as 9 years of age. A soulless body wouldn't go to 4D and Organic Portals will be left behind too.
I guess whether the child moves up or stays in 3D would depend on the state and maturity of the child's soul. Also, bear in mind that the parent-child relationship is a genetic one, that of physical bodies, not souls. Past time connections do happen but a mature soul can be born in a family that has not matured enough in order to graduate - and vice versa.
For the above reasons I don't think children will automatically graduate to 4D just because their parents are ready for the transition.
No, not all of 3D. Only those who have learned their 3D lessons and polarised sufficiently for graduation will move up. Those who aren't ready will have to repeat the cycle.
Session: 9 Aug 1997