To heat or not to heat is closed for me.
It is ALWAYS up to the individual.
You aren't going to know if your chickens would have fared as well, or better, or worse without heat and I won't know if mine would have fared as well, or better, or worse with heat

You are ready and being prepared is NEVER a bad thing. If it happens that my girls look to be suffering, I'll be scrambling to put something together.
Bruce