The Reds led 2-0 at the interval and a late flurry of four goals in the final 10 minutes added some gloss to the scoreline against a Blues side that were competitive and enjoyed a spell of decent pressure in the second half.
Yet there was much to enjoy about the performance from Darren Fletcher's side, who had three debutants at this age level, including goalkeeper Charlie Hardy, who made an early save to deny Joseph Ralph.
United took control though, with Junior Brown thwarted by a diving stop from Szymon Terenowicz and Gabriel also having an attempt kept out by the Blues keeper.