Newly minted 1K here.

Piggybacking a quick question here regarding the 1K benefit of complimentary Economy Plus for 8 travel companions.

Is there a way for me to book a J ticket for myself and a Y ticket for a companion(s)?

I'd like to travel more with my son who is 9 and I think he's old enough to sit in Y by himself. He's got lots of flight experience and it's been mostly in J but he's a little guy and doesn't really need the space. On premium transcon flights he sometimes doesn't even recline his seat preferring to play video games the whole way and he's taken a meal exactly one time instead opting for a snack box the rest of the time. It'd be nice to book him in Y but up front closer to the J cabin. We also took two international vacations this year with our babysitter, said 9-year old, and 1-year old. We all flew in J but it was a lot harder to find itins with four contiguous seats. It'd be much easier if we could stick the three in Y and wife and I in J. Not to mention the cost savings.

I spoke with the 1K desk and they said what we all have to be in the same cabin per PNR and we also have to be on the same PNR to get the free Economy Plus access at booking. If there's no way around it, then 1K isn't really worth it since I'd rather pay for guaranteed J rather than rely on upgrading.

--EDIT--

Would this work?

Purchase two J tickets on one PNR. 1 ticket for my wife, 1 ticket for the babysitter (both general status).
Purchase three Y tickets on a different PNR and select Economy Plus seats for free. 1 ticket for myself (1K), 2 tickets for kids (general status).

When we get on the plane, switch seats with the babysitter. I could be at the mercy of a strict FA regarding the seat swap but it should be easily explainable, no? Even with COVID we are in the same family.

Thoughts?