They will tear up your yard and have been known to kill cats, kittens and even small dogs. They will kill chickens and eat them, and they have small hand-like paws that can get through chicken wire. They carry a number of communicable diseases and parasites, including rabies. They can be very aggressive and will bite and scratch - you, your kids, and your pets.
You may have a local wildlife center that can help you discourage them from coming into your yard and from getting under your deck. There is information on raccoon deterrents on-line. Once you get them out from under the deck, seal the space. Clean up all dropped fruit from trees and put garbage in critter proof containers or keep the cans in the garage. Do not feed pets outside.
In California, it's illegal to trap and relocate wildlife. Raccoons generally live in family groups, so if you relocate one, the chances of survival are not high. Not relocating them also limits disease transmission. You can hire a commercial trapper, but their only option here is to kill the raccoon.
We have raccoons here that use the storm sewers to travel around. I'm very careful to get the animals in by dusk and no food or water is left outside.