you don't need an air lock. It will be fine, BUT you prolly really don't want to wait till the day before to carb it. You will have a flat beer with a great head. You would be better off hooking the gas up at least 4 or 5 days before the party. I force carb all the time, but after the 1st day, i dial it back down to serving pressure and let it sit a minimum of 5 days. Usually 10 though.
Also, by the time you hit the secondary, there really isn't any fermentation taking place. The yeast are just cleaning up after themselves. It is more for clearing and conditioning.