You seem to be avoiding question about childrens' ages. Again, children 14 and under must be seated w/ adult in same cabin. If you try to circumvent rule, you'll probably lose upgrades and possibly better seats together in back. If all your children are fourteen or under, it's black and white - four upgrades or no upgrades.

From GS benefits wiki thread:

• GS can confirm any waitlisted instrument-supported upgrade (miles/co-pay or PlusPoints) within T-72 hours to flight departure provided at least 3 (three) J class premium seats remain for sale after the upgrade is processed and they are at the top of the waitlist. Within T-24 hours only 2 J class seats need remain. Since fall 2022, agents have been saying its valid for "one exception per PNR," thus only one-way. Having separate one-way PNRs for a round-trip may help, but some agents look for this.