Or just start off with a proper number of days. Two weeks seems so short, especially if you get sick. 15 days total seems about right.
Facebook, Google, etc commonly use the contractor technique, where anyone you want to work for you but not give benefits becomes an independent contractor, or works for a vendor. Eg, the cooks in the Facebook kitchens.
Also there's no reason everyone has to receive the same amount. Indeed that would be very unusual.
Edit: And, you are supposed to use them. Not making sure your employees spend their holiday days can land at least the company if not the employee as well in legal hot water.