The first time is going to suck, it's not gonna be fine. Lol. Might as well expect that it will suck and plan for a better experience the second, third, and from there on.
After all, it's only his first sexual experience that will set the tone for the rest of his life with someone to whom who he's pledged his entire life and soul.
I'm sure you won't disappoint duff! Just try your absolute highest and hold yourself to the highest level of performance -- expect nothing less. I'm sure it will be world-class and phenomenal.