The girls get a warning or three before I turn the vacuum.
Then if its not picked up then it gets sucked up, its kinda fun sometimes to watch them panic and clean up all their toys in a hurry.
Same happens when they are asked to clean their room. They get a certain amount of time to clean before I start the vacuum at the beginning of the hallway, they have until I get to their room to clean it, then whats left on the floor is fair game. They're starting to get the idea that mummy means business when she asks them to do something.
So, yup lego would be sucked up.

But if it were something of mine or something I really loved, the vacuum would be in pieces with me trying to find it!