To be crystal clear: your child is not and will not be ticketed to travel as an unaccompanied minor unless you choose to do so (which would be folly as you are travelling together).
Absolutely not a problem. Every passenger has his own ticket. Whether booked into the same or separate PNR's is irrelevant. You may need to do the child's ticket on the telephone, but that is a minor issue.
You will not be able to check it online (not likely anyway) and will have to present yourself with your child for check-in. JL will make certain that the child boards with you, just as it would if you booked the two tickets into the same PNR.
Finally, JL can place notes in the two PNR's pointing to the other PNR for administrative convenience.
Do not waste money transferring points as it will not make any difference whatsoever.