Does Kid#2 529 plan amount need to be entered in Kid#1 FAFSA application?

Yes. Unless the 529 is in Student #2’s name (or a non-parent is the account owner) it has to be reported as a parental asset. It’s still money available for Student #1 as all you need to do is change the beneficiary. It doesn’t matter if you don’t WANT to use that money for their college.