Is it better to cancel an order that will ship late?

Right now I am selling jewelry via FBM and don’t get many orders at all. Most items I ship the same day but there are a few items that I don’t hold in stock and are shipped to me. The problem is that the vendor is late shipping the ring to me and I have to ship the ring to the customer within 2 days… I’ve gotten about 4 orders this month, and it will be at least a few days, or even a week, late shipping it to the customer. On any other platform, I would just message the customer and apologize and ask them if they want me to cancel. What should I do on Amazon? Is it better to have my account dinged for shipping it late (so a 20% late shipping rate) or cancelling the order? I also want to do right by the customer. Thanks