I am so sorry to hear about your tragedy. My bassett hound was 14.5 years old and getting very sick. I started researching new dogs 6 months before she died, because I knew I couldn't live without a dog in the house. Too quiet. No one to love you unconditionally.
It sounds like you have a good plan and arrangement with your sister. I really hope you find the puppies you are looking for when you want them. I also pray that you will be comforted by all the great memories Poppy gave you.
Charleen and Cav's: Pippin (ruby male), Merry (b&t female), Luke (blenheim male) & Jolly (tri male puppy)