If you did a custom white balance in the field, then this should be picked up by ACR automatically.
At the end of the day, the raw image *is* the photo. I tend to completely ignore whitebalance in the field as I prefer to get this how I want it in a calibrated-monitor environment with Photoshop.
If I need to shoot JPEGs, then I start to worry about whitebalance in the camera!
Andrew