SAS EuroBonus - *A Award seats in Economy Extra?

I'm redeeming some UA MP miles for a trip PDX-TXL in May. Originally I was booked on LH PDX-FRA-TXL but they changed their scheduled and pushed my trip back by a day which is not ideal for me. The only other option that United is offering me is to fly PDX-SEA-CPH-TXL. I'm somewhat apprehensive about this option as I'll be traveling with a 4 month old so the additional connection (once in SEA and once in CPH as opposed to just once in FRA) is not ideal.

As a Star Gold, is there any way to book my award seats into Economy Extra? Or upgrade 3 seats from award to Economy Extra? I'd book business seats if I could, but the lap fee for an infant is so high (10% of the $10,000 fare) that I'd rather just book him an additional seat.

Thanks in advance for your assistance.

There is no way your UA miles can get you in to Economy Extra on SK. THe award booking class is P but not open to UA unfortunately (if havn´t been changed in the last few weeks).
They might sell you a cash upgrade at SEA (SK ticket counter). Economy Extra on SK Airbus is 2+3+2. The bulkhead 3-seater would be ideal for you.
CPH is a good airport to transfer, you will have nice facilities to take care of the baby at the lounges etc. But I do understand your point about keeping the transfers down. Also each transfer increases the risk of misconnecting.

Apart from that SK is a very friendly airline when it comes to travel with kids. Parents typically get far more attention than elites ;)