"Surf Uppers", or "Surf's-Uppers" irresponsibly comes to mind . . . but then where would you go for "Downers" (if it's even clear what "downers" are)? On the other hand, if the Uppers are long enough, you wouldn't need the downers. Besides, people don't ask, "What's DOWN?"
They ask, "What's UP?" and if you're an aficionado, you answer "SURF'S UP!"
And there's the whole silly etymology.

In the evening, you could offer "SurfSuppers" to hungry Uppers OR Downers.
(Please do not embarrass me by sending an additional $100 for this last line)

Chuckledore (technically a "stranger", but while I'm strange, I don't
really feel like a stranger here. . .)