So an update, I.booked the tickets as two one-ways, without issue and I greatly appreciate your collective advice.
Interestingly, the American Airlines phone rep did ask how we were getting home and I explained that I was booking the return portion via Alaska Airlines.
She laughed and said that she had no heard of a passenger using two different airline accounts to book a trip but more power to me.
Alaska didn't even make a comment.
Thanks again for all of your advice!