I've been owned by cats for my entire life. I have two now.
Please keep in mind that this is a LONG commitment. Cats can live for as long as 20 years. They need annual vet check ups and immunizations. You need to ensure that they are treated during the warm seasons so they don't get fleas or ticks.
When you visit the shelter, talk to the folks there and let them know just what you are looking for. I stongly recommend that you get an older kitten who has already been spayed/neutered, or a younger cat. If you're looking for a cat to be strictly indoors, a kitten or cat who has never been outside is a good idea, since they probably won't be as likely to take off out the door. Indoor cats live longer and are healthier. I recommend keeping your kitty inside.
IF you decide to declaw, you should ONLY do this on a kitten. Do it during the spay/neuter. I really don't recommend declawing. It is cruel. You are literally having all of their fingertips chopped off. But if you decide that is what you want to do, DO NOT DECLAW an older cat. It can cause serious behavioral issues and litterbox problems.
It is very likely that the rescue center will already have an declawed, fixed, very kid-friendly young adult cat. If you so chose, you could completely skip the entire kitten age (which has its perks). So that's something to consider.
Regarding what you need to do at home, there are plenty of books out there about preparing your home and family...but first and foremost, I advise that your kids spend at least a couple of hours playing inside a friend's home with their cats. You don't want to get a new kitty home only to find out that your kids or spouse are allergic!
Best of luck!
ETA: I just wanted to respond to the person who said cats are "not good kid pets."
This is utter nonsense. I mean, I've never heard of a child being mauled to death by a cat...
I've had cats in my life since I was a toddler. When raised around kiddoes they are extremely tolerant. Yes, they might bite or extend their claws when a child gets way too rough, but the child quickly learns to be more gentle.
I have two boys and two cats. My 8 year old cat is just 6 months younger than my youngest son. Taylor doesn't remember a time without him. We also have a 6 month old kitten. She lets my boys pick her up, carry her around, rub her belly, and has only scratched accidentally when playing.
So...bottom line, don't listen to people who say that cats are not good for children. They are wonderful for children, and far simpler to maintain than dogs.