Ninety children with critical congenital heart disease demonstrated moderate correlations between cardiovascular fitness (VO₂peak) and daily physical activity (r = 0.36), while fitness showed weaker links to motivation and confidence levels (r = 0.25). Notably, parental sports engagement predicted children's athletic participation equally for both mothers and fathers (r = 0.23 each). Children with single ventricle anatomy exhibited significantly impaired cardiorespiratory capacity compared to those with two-ventricle hearts, though other behavioral measures remained similar. This research addresses a critical gap in pediatric cardiology by quantifying how congenital heart architecture affects exercise capacity and family dynamics around physical activity. The findings suggest that while severe anatomical constraints limit peak performance in single-ventricle patients, psychological factors like confidence and parental modeling remain intact across heart defect types. For families navigating these conditions, the data supports encouraging age-appropriate movement despite fitness limitations, as motivation pathways appear preserved. The parent-child activity correlation particularly highlights how family sports culture transcends cardiac anatomy, offering a behavioral intervention point that doesn't depend on surgical outcomes or physiological repair completeness.