I can easily understand about your situation. just looking at those photos is haunting

....... They look soooo sad, & they probably have never known what it's like to be pampered. .........I wouldn't want to be in your shoes right now

..........I don't have any advise except, that if you do it keep them completely separate from your pets, or your home til you get a vet check, which I'm sure your already aware of

........My sister got a Chi. at Petland a few yrs. ago , against my advise,....... long story short........ he kept sleeping & was listless so she took him to the vet., he had parvo & died within weeks.
No matter what you do, either decision is a tough choice, good luck
P.S. Stay out of those stores