This question comes up regularly, pretty much every week. You can ask when you check in, they may allow it & they may not. I use the online check in, some restaurants say we could add another guest, some say you can’t. Chefs of France is often fully booked so they may not be able to accommodate extra people. And you won’t be turned away. They will seat 3 of you no matter what. And if you choose to walk away if they say no, you may be charged the $10 a person no show fee. So have a plan what you’ll do if they say no. Definitely keep looking for the spot for 4, you have plenty of time. Many times people cancel the night before as their plans change, so you might even get something last minute.
You can even look for a party of 1 or 2 at or near the same time & ask to be seated together, or close together. Many restaurants have limited tables for 2, but Chefs has quite a few, many are close together too.