Small children, especially when they are being a little bit naughty or mischievous.
It's usually a cute or funny word, and it's not very serious.
Examples:
The scampies were playing in the yard.
She's a little scampies, but we love her anyway.
The scampies ran around the house, laughing and shouting.
The scampies made a big mess in the kitchen.
The scampies were up to their usual tricks.
I can't stay mad at those scampies for long.