Hiya,
You could try either of these
Get your kids friends to wear shorts when they come round - they'll soon stop her jumping up
or.......
Tell them to bend down or crouch when they say hello.
This is a common problem with my other dogs, Labs are soo cute as pups everyone wants to say hello to them. Nice with a cute puppy, not so nice with 30kg of wet, stinky adult!!
Ali