The only way you can change the fare code now is to buy up. So your friend will have to call the 1K desk and ask for a fare that a SWU can upgrade you on (W). Then he'll have to pay the change fee and the fare difference, per passenger. Then, he can apply the SWUs.

Or...he could use miles, which is what I'd do. Then you're only paying an extra $500 a seat - and that's only if the upgrade clears.