I have a reservation of 4: 1 1K and 3 GMs. I'd like to split off the 1K and apply an RPU. However, there is also an outside chance that we will want to do a SDC. By splitting off the 1K, will we lose the free SDC for all; or will a phone agent see that the itinerary was split and be able to waive the fee for everyone?

I have seen posts discussing other perks that a phone agent can carry over, but I'm not sure if anyone has experience with SDC in particular. TIA.