I hate to break the bad news, but if the cats have fleas, so does your house. Sorry.
For your home, the safest thing to use is a growth inhibitor such as methoprene, which is now available as Precor. (Make sure 1.2% methoprene is the only active ingredient such as in the Precor IGR, and NOT Precor 2000). This is a hormone which prevents the fleas from transitioning from larvae to adult. It doesn't kill adults, but it prevents the eggs from completing their lifecycle so in 1-2 weeks, no fleas. It is extremely safe for cats and people and the residue stays effective for months.
I used this with 2 treatments of Advantage/Frontline/whatever and in 3-4 days, there were no fleas I could see. If you were to skip the Advantage stuff, the methoprene would eventually kill off the flea infestation (because they couldn't transition into adults) but it will take 1-2 weeks. Just be sure to spray carefully everywhere with the methoprene if you use it alone so there are no coverage gaps.