I can't give you any advice, but I can share your worries. My daughter, who turns 3 next month, is due to have open heart surgery a week after her birthday......she has Ebstein's Anomaly of the Tricuspid Valve. The whole thing has me worried, but......I feel that the Mayo Clinic (Rochester, Minn) is the best in the world, & that the surgery will probably go fine.
Still, 3 yrs old is a young age, but.......maybe old enough to bounce back from surgery quick. Keep us posted here, email me if you need someone to talk to about it.