Welcome to the vagaries of operations. Working in operations for...

Welcome to the vagaries of operations. Working in operations for over 30 years now, there's nothing out of the ordinary with the change in timings or plans. It happens all the time.
Somethings are out side a companies direct control.

With regards to the change regards timing of EPT & 3D aquisition..having worked on a similar project recently, you get all sorts of advice.
The "perfectionist" --- never do the two at the same time..you might get noise on the seismic/noise on the downhole guage readings etc and the "pragmatist" - yes there may be some effects but we know that and we'll live with it!
Ultimately, its a management choice - understand the risk and manage operations accordingly.