I'm so sorry you're going through this. It's a heartbreaking decision to make, but please know you're making the right decision.

I went through this with my dog last August and we used Loving Kindness Vet to come to the house, administer the drugs, and then take her for cremation. They were very compassionate, made sure we understood and were comfortable with what they were about to do, and gave us the time we needed to say goodbye before we called them over to get started. I'd really recommend them if they're available.