Turtles in Households with Babies and Small Children

>The girls really want a pet
>but we are not ready to commit to the level of effort required for a dog
>or cat. 
>
I would put the effort of having a turtle at about the same level as
having a cat. Turtles need a proper environment, daily attention to
their needs and diet, cleaning of the tank; but they don't need to
be walked, and they don't mind playing by themselves, and they don't
depend on people's love to enjoy life.

>Are turtles safe for young children?  (do they carry any unwanted germs,
>etc.?)
>
Like all animals, turtles carry germs. Some turtles carry salmonella.
The risk of getting salmonella is estimated to be a fraction of the risk
of getting salmonella from eating chicken and eggs. However, just like
in the kitchen, good hygene, handwashing after handling a turtle,
keeping the turtle enclosure clean, and keeping turtle feces away
from children's mouths is essential. (Find more on this topic at my
web page and at the link to Melissa Kaplan's page.)
Turtle cleaning chores should not be done in the kitchen.
I have a two-year-old daughter, and I have several friends with small
children. My daughter is not allowed to play with the turtle by 
herself, and we always wash hands afterwards. Until she was old
enough to keep things out of her mouth, she was not allowed to
handle the turtle. 
Unlike a cat, a turtle will not protest, cry, or bite back when
mishandled. Poking, pulling legs, pushing around are things small
children do to animals out of curiosity, but that natural curiosity
can be unpleasant for the turtle.


>How long do they live?
>
A healthy water turtle lives 40-60 years; a healthy box turtle over 100.
Definitly a long-term committment.

>How much care do they need? (Can they be left with adequate water and
>food for a weekend?)
>
Yes. If you have a proper setup, you can leave the turtle for a weekend.
For a water turtle, you can set it up so you could leave for several days;
with a box turtle, if you are gone more than a couple of days, someone
would have to go clean the water dish.
My personal setup allows for weekend outings, and when I go on vacation,
I have someone go by every other day.

>How much love do they need?  (I'm afraid the girls might lose interest
>after awhile).
>
Turtles don't need as much love as they need the attention of good care.
If you think your girls will lose interest, and if you are not interested
in having a turtle for yourself, then a turtle may not be the right pet
for you. At least until children go to highschool, any pet of the children is also
the mother's pet. You will be taking care of the turtle, and you will have
to be responsible for it for quite a few years even if your daughters
keep being interested in teh animal.

From my own experience (as a parent, turtle-keeper, and a child), good
pets for small children are aquarium fish (little care, inexpensive,
shortlived), small rodents (shortlived, inexpensive, furry, cuddly,
intelligent), cats/dogs (family pet), or parakeets (they actually live
quite long). Small snakes also make excellent pets for children, but
many mothers don't care for them.

Personally, I think that a turtle is not a suitable pet for a small 
child, but it can be a wonderful pet for adults with small children.

I hope these ruminations answer your questions and help you make 
your decision.