Or you could make it a semi-legitimate front. A company where only a handful of employees know that they are connected to the mob.
Which means that most of the employees will be innocent bystanders with no idea why the shit is hitting the fan. When the PC infiltrate they don't find that the main office is full of mobsters run into Cathy from Accounting and Jed from PR - people who have no idea why the PCs are there and can't answer any of their questions.
The classic "front" has to be the one in The Firm by John Grisham. It's a law firm where the head of security and the senior partners know that they are a mob front, but the bulk of the employees (janitors, paralegals, junior lawyers, etc) think that everything is a legitimate firm.
Then there's the classic Mack Bolan series where books 1 - 30 (or was it 1 - 60; it's been a while since I found that series at a used bookstore) had him at war with the mafia. He shot his way through various fronts - record companies, strip clubs, a savings and loan outfit that had a loan shark division, a bakery (that included drugs in their bread deliveries), medical clinics (that were mostly legitimate but had rooms set aside for "Mob Doctor" type cases), realist companies, travel bureau - the list was near endless as the author tried to show how the mob had its tentacles everywhere.
Richard