Pumping question

Sabrina • Married 04/08/16 💍 Expecting our first : May 16th💖 Army wife 🌹
My son is 2 weeks old and is EBF on the boob. I have to be out tonight from 5pm-10pm. I have three 2.5 ounce bottles for him but he'll probably only need two of those. My question is, if I pump once around 7-7:30 in the bathroom will my supply by ok? Or should I pump twice? It's a work event so I really don't want to leave twice. Thanks in advance!