Craig, the good news is that treatments for TOF have advanced greatly in the past few decades. If you haven't already accessed this web site, it has a lot of really good information:
/www.nhlbi.nih.gov/health/health-topics/topics/tof/If you know the name of the surgeon who will be treating your grandchild, it may be informative to google his or her name, also.
Best wishes to you and your family as you move forward to face this new challenge.