Cherry Orchard started positively and were full value for their interval lead despite wasting a terrific chance on seven minutes.
The clever feet of Mark Hughes played Lee Collins through, but Town keeper Craig Hyland was smartly off his line to make the save.
But Orchard got the reward for their early endeavour with the lead goal on 24 minutes.
The defending from a throw-in was poor and Sheppard finished superbly off his right foot after his initial shot had been blocked by Des Hope.
Longford chased the game hard on the resumption and they hit the post on 58 minutes, defender Daniel Ennis heading against his own framework from Thomas Crawley’s cross. Orchard keeper Sean Brazil was named man of the match for terrific saves from Daniel Purdy and Jamie Duffy either side of their getting their second goal.
That came on 77 minutes. Hughes again was the provider, playing 18-year-old Caul through and he drilled his shot beyond Hyland.
CHERRY ORCHARD: Brazil; O’Sullivan, Byrne, P. Collins, Ennis; Caul (Byrne, 82), McNeill, Moran, L. Collins; Sheppard (McNeivin, 78), Hughes (Rooney, 90).
LONGFORD TOWN: Hyland; Dowling, Hope, Flood, Crawley; James, Gillespie (S. Skelly, 81), Salmon, Lee; Duffy; A. Skelly (Purdy, 29).
Referee: Adriano Reale (Kildare).