Yes to cats for happiness : - ) Ours actually help DD write because she hates it so much, but at homework time they rub against her and purr and she always ends up writing a sentence or two about them. They are the stars of her daily journal.
You could get an older, laid back cat AND a kitten. It's always nice to have two in the house for companionship if you have to go away, even for a night or two. And our older one did the litter box training and will give the little one a swap over the head if she tries climbing up the screens or something.
I don't know what it's like where you live, but where we are there are a couple of malls with "no kill" shelters and you can visit them a few times and one has a room where you can be alone with them to see how they act with the child.
The county shelters also have their adoption days, we got our kitten there. We went for one particular one we saw on the internet but when we got there, that cat wouldn't have anything to do with DD but another one snuggled right down in her arms right away. She loves story time and sleeps with DD every single night.
I found that out about the volunteering also, I was told age 12.
When I was DD's age I would not have been able to visit shelters without being completely devastated, it's taken me years to get to this point...but she can handle it pretty well.
I would say that (people usually feel strongly about this one way or the other) but for a sensitive child I'd keep the cats indoors. Ours are completely indoors but last summer the older one got out and nobody was going to sleep in our family until that cat was found and safely back inside. It didn't take long, she was just at the side of the house being scared and confused, but it's worth a thought.
