For one dog my parents got the poison and did the injection, the dog dying in my lap, peaceful enough (and very sad—-we had many adventures together). For another dog-companion, this in my adulthood, our regular vet was kind, considerate, and matter-of-fact; verifying we wanted to kill our old dog, injecting the poison as we held our dog, and giving us plenty of time to grieve. If it had been just me I’d have stayed to help move the body, or at least watch, for the extra connection to the lifecycle. I have so many positive memories of both dogs, and accept that I will be part in deciding how and when our current dog dies. I hope you find the right professional to help you and your companions if they don’t conveniently die in their sleep.