It may be a bit late (or approaching that point) to have one of your family members move one of their kids or someone into your room (or if you have kids with you and DH, you could swap kids on the reservations to keep the numbers in the rooms the same.) If you had even one repeat cruiser in your room, regardless of their age, then everyone in your room would be eligible for the repeat cruiser benefits, including the right to book Palo, etc early. First time cruisers can only book at the 75 day mark. Repeat cruisers can book at the 90 day or earlier mark, depending on their
castaway club status.
Short of that, I'm not sure you'd be able to book a dinner for just the 2 of you at the 90 day or earlier mark that the repeat cruisers will be able to book.
I don't know if it will help, since your rooms are linked, if you pay in full by the time they get to book, and have 1 couple linked with you make separate Palo reservations including 1 of you and 1 of them in each reservation. Then, when it's time to do to dinner, they could go to one reservation, and you can go to the other one. I've been linked to new cruisers before, but she joined within the 75 day booking window so we never tried to book her in Palo before she was eligible. Each person can only have one advance Palo reservation per meal type (dinner, brunch, tea), so they can't book multiple reservations for themselves and give you one. When you book, you are always in the lead slot on the reservation, but you can designate who will be eating with you, and it generally shows you the list of all adults linked with your reservation.