In need of…um…a crime?

If there is something specific to the area, that would help set location. So, if small town, the local bank name here. If say, Seattle, the space needle. If you just want a big recognizable thing, Maryn already listed some great ones.

If you want a twist on it all you could try "show business"

If they're school-aged, then a bank or other major institution seems far fetched. Why not keep it within their own milieu, something that may not have financial gain but has relevance to them like the principal's office or the storage shed of the weird janitor (because he seems to be going in and out of that place at all hours). If you want to expand outside their school, you could consider a rich peer's home or place of business.

First ask yourself why they want to do it. If it's not for money but for the thrill, then it's important the crime scene is really relevant to them.

the vault where they store the formula for Coca-Cola.

The National Democratic Headquarters...