iPhone gps app

you mean track the iphone by gps so the user doesn't know there being tracked ?

see
http://gpstrackr.mobi/

Well that would be what she is looking for, but she does not want to jail break the phones. Are there any apps that "run silently" this without jailbreaking?

its on the app store !
https://itunes.apple.com/app/gps-trackr/id376564399?mt=8

so where have you seen jailbreaking ?

She wants one centralized point from which she can trak both phones

Hello try this, it is popular, free and easy to use
https://itunes.apple.com/us/app/find-my-iphone/id376101648?mt=8

would not that require her to log into separate icloud accounts for each kid?

http://www.mobile-spy.com/compatibility.html
here is an example of one that runs in stealth mode but requires jailbreak

would not that require her to log into separate icloud accounts for each kid?

Not necessary. All she has to do is to use the same credentials (email, password) when setting up the app

-on the kids iPhones

    -your boss can either track them from the computer by going to www.icloud.com and sign in with the same apple ID and password
or download this app  find my iPhone https://itunes.apple.com/us/app/find-my-iphone/id376101648?mt=8&ign-mpt=uo%3D2 on her iPhone
 and sign in with the apple ID

if every kid has a Different apple ID then she has to use multiple browsers for each kid
lets say that she has 4 kids
first kid: www.icloud.com from google chrome
2nd kid: ================= internet explorer :S
3rd kid : ================= find my iPhone app on her iPhone etc...

The best app to track any apple device is, by far, find my iPhone. As long as the kids have their location services on, then you can track any of their apple devices by logging onto find my iPhone online. If he kids have multiple apple id's then you can keep multiple windows open,  with one window assigned to one child.