I think seeding alfalfa in ph that low is high risk. If you can utilize the oats as baleage, I would:  seed oats this spring; harvest as baleage; come back and seed a second crop of oats in mid-to-late summer; take a second crop of baleage; then seed your alfalfa next spring.   I think it is going to take a whole year to get that soil pH up to where it needs to be for the alfalfa.  That is my opinion.

An alternative idea:  if you can utilize the grass, then skip the alfalfa and seed a straight seeding of grass. I think you should be able to do that this spring.  A solid seeding of meadow fescue or high quality tall fescue should do fine in that scenerio.