Well I have "fostered" many kittens with my adult cats. Most of the time they hiss at the kittens for a day or two, but they eventually work it out themselves. Take it slow, and make sure you observe the interactions between them. They will work it out. My youngest cat is a rescue. We made the decision to keep her the day I brought her home, and she wasn't intimidated by my two olders cats behavoir. But keep in mind you will probably have some behavioral issues with the older cat, like territorial marking (peeing), pooping in the house, scratching things, etc.
at 12:26 AM on May. 6, 2009