From personal experience, using UR->Travelocity for United flights has allowed me to make changes as if I booked directly through united.com. I didn't have many issues moving flights around (usually with the standard $75 fee).

But think about the cost/benefit of this. You're playing with your boss's travel. How many UR points could you score? @2x, for $500 fare, or $2500 fare. 1000 or 5000 UR points. Is that worth potentially making your boss screwed in re-scheduling flights?