I would give them some time, and if you can spend a little more time with them. If they are open to it, after some time, bring one of your dogs over with you.
A senior dog from a shelter sounds great, but folks don't like the pain of losing a critter, and that is just a fact. It doesn't matter if it is 3 years or 3 weeks, when they lose the dog it will be really hard. You can never guarantee anything, but if and when they are ready, I would suggest a young adult, a pup through the puppy stage, that they can polish up the obedience on, or that you can place the dog with a trainer for so many weeks or months and then give it to them, as they may not be able to spend a lot of time training.
Of course then you have to consider the disposition of the dog if your aunt and uncle become unable to care for the dog. Maybe a cat would be better. It could seriously reduce that empty feeling of a home without a critter, and will be easy to care for, and still give the folks a reason to get up and love a creature with a distinct personality of its own.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.