Congratulations on the new job! Peds cardiac is super challenging but super rewarding. I would brush up on some of the most commonly used medications, both daily ones and emergency ones. Here are some that come to mind:
Milrinone (continuous infusion)
Epinephrine (continuous infusion)
Nicardipine (continuous infusion)
Dopamine (continuous infusion)
Amiodarone (continuous infusion)
Do a little review of EKG rhythms. There are good websites out there, I just don't know any specific ones offhand. Maybe check Khan Academy. Obviously know the big ones - asystole, V-fib, V-tach. Also look at heart block, SVT, and junctional ectopic tachycardia.
Finally, I would recommend this website as a easy-to-read review of heart defects and surgical repairs: Congenital Heart Disease - Cove Point Foundation | Johns Hopkins Children's Hospital
And here is my favorite "pocket sized" reference book for congenital heart disease:
Illustrated Field Guide to Congenital Heart Disease and Repair
Make the most out of your orientation, don't be afraid to ask stupid questions. Find resources where you can look things up that you don't know. Good luck!