Another exquisite build-up led to Ezekiel Fryers crossing for Will Keane to head off target.
But United were unable to get the second goal some enterprising play merited and, instead, City started to enjoy more possession. Amos was still largely untroubled as he comfortably fielded a free-kick by Denis Suarez after Fryers was harshly booked for a foul.
Amos fisted away one cross from the lively Jeremy Helan and Michael Keane managed to stand firm on a couple of occasions, once getting a crucial touch with substitute Jordi Hiwula threatening but Will Keane, ploughing a lone furrow in attack, kept the City defenders on their toes.
And the striker managed to get his pass away to late sub Giverin in stoppage time, with the youngster running through and clipping his finish inside the far post just as he was being closed down by the defenders in hot pursuit. It was a fitting end to a fabulous campaign for United's second string, who have been a joy to watch all season. Even a pitch invasion failed to take any gloss off the occasion.
United: Amos; Vermijl (Giverin 89), Keane, Wootton, Fryers; Brady (Fornasier 82), Tunnicliffe, Pogba, Petrucci (Thorpe 70), Lingard; W.Keane. Sub not used: Johnstone.