Nobody ever died from going SLOW and easy at letting their polyship unfold. BREATHE.
You do not have to be expert. You have to be honest, open, and communicative.
Here's my poly playbook for how I stay in right relationship.
Apart from reading posts here, and books like Opening Up or Ethical Slut I would suggest online resources like
The Opening Up website that matches the book has some free worksheets you could think about doing too in preparation.
I really don’t want to have to considered what I’d do if either of them told me I had to choose.
Easy. Each one of you?
You choose YOURSELF and what is best for your health buckets in the long run
-- mental health, emotional health, physical health, and spiritual health.
Everyone holds their own bag(gage).
You do not need to fear conflict.
Conflict is simply people in disagreement. It is opportunity for growth and better understanding of self/others.
You could use conflict resolution methods to try to find the happy medium. We don't all have to have the happy STUPENDOUS each time.
Or you could agree to disagree and let it go.
Nobody is conflict FREE. Except dead people! (I joke to keep it light.
The goal is not to be conflict free but to handle the conflicts that pop up (and they will --- Life IS) with some ability and grace so you all fly your polyship together WELL.
You will be ok.