I know you're asking to pay to offload this duty, but I have a suggestion that perhaps you should consider. I would encourage you to consider keeping those duties for yourself, and add a new application to help protect them all the way around.
Deep Freeze by Faronics - http://www.faronics.com/produc...
This product will let you create the perfect configuration for your parents, then 'freeze' it in place. They can have places for documents to go that you can edit and change and so forth. But, if you get infected with something, or an application installs something extra you didn't want, or your browser gets fouled up, you reboot your computer and Deep Freeze makes your system revert back to what it was before those changes took place.
If they aren't changing or updating their system regularly, they just wait until you can do that for them, on your schedule. If they have problems, they reboot and get a working computer back. You'll still want to backup their documents, but you can use a cloud solution for that, so it'll be set-it and forget-it, except when it's time to pay the yearly bill.
It's juts something to consider. Again, I know it's not the hands off solution you're thinking about, but as your parents get older, they'll appreciate your help all the more. It lets you still use this to be connected to them, and feel more like you're taking care of them than pushing that duty off on someone else. Your time is worth way more than the money you spend on them.