Need some opinions from the Cat community. .?

I have been feeding some feral cats for several years. I have severe allergies, and cannot have animals in the house. Last year, I took one to the vet because it seemed so ill. The vet said it had a severe case of feline HIV, and I had the cat put down. The vet said that it was likely that the sick cat had infected the others as well.

Now my favorite, whom I can actually pet, is showing advancing signs. We will be vacationing in mid-May for over a week. I worry that the cat will not survive until we come back. (I have a neighbor kid put out food every several days.) I don't want to have the cat put down unless it's absolutely necessary, and I don't want him to die alone and abandoned, either. Any thoughts?