I think i've commented on this several times .. but yes.. you have to call the operating airline and explain that alaska can't sell your airlines tickets and thus they can't sell a lap infant fare. Thus they have to create a dummy adult booking tag it with an infant fare and then tag that infant fare to your award fare. then delete the adult fare. It works 60% of the time 100% of the time. I've done this with Qantas, Fiji and JAL. Be ready for LONG and potentially multiple phone calls.

Qantas. Seemed easy .. was a cluster once we got to the airport. Took 3 hours at the check in desk for them to figure it out. I even had a record locator but it never ticketed because the agent put the wrong routing in the infant ticket to an impossible routing.. I guess if we didn't get a dumb agent it might have worked.

Fiji: super easy took like 2 hours on the phone no issues

JAL: Also super easy. 3 hours on the phone though. And holy expensive. They charge 10% of the full fare ticket.. so for us it was $1200 to add the infant on our roundtrip business award. Haven't flown this yet but not anticipating any issues.

My advice.. book with united until they are two if you can. United you can ticket the infant when booking even on partners. Its super easy