I'll probably be linched for saying this, but I think letting cats be alone for the weekend is fine. I litter my house with water bowls, leave plenty of food out, and they are fine.
If a cat gets into a closet or a drawer with string or finds some poision hidden by a previous tenant, or gets outside without anyone to let it back in, or gets suddenly ill, then the cat could die while you are gone. But how likely would a cat-sitter be to catch each of these things?
I actually had someone come over when I was gone for something like 5 days, but he really thought my cats would be fine without anything done to them, and he didn't end up doing anything. They were fine. (They're fantastic with using litter boxes and I don't remember how many I put out, but it was a lot.)
My current preference is for cat sitters to come over once every other day, but the one I used a few weeks ago came over every day (and I have cat sat by going to other people's houses twice a day).
There are many systems that work.
Leaving cats home alone for the weekend can be one of them.