John Morling’s side had defeated another local side, Louletano DC, 5-2 on Tuesday and this revamped Irish side raced into a three-goal lead.
Millwall striker Conor Wilkinson fired the Irish ahead on 23 minutes by swivelling on the edge of the box and burying a low shot into the bottom right-hand corner.
On the stroke of half-time, when Wilkinson was hauled down in the box, up stepped England target Grealish to convert the penalty.
Alan O’Sullivan from Home Farm crowned his first start in an Irish jersey with the third goal two minutes after the restart before the hosts pulled a consolation back from the spot on the hour.
Morling said that the week-long exercise proved ideal preparation for the UEFA U17 elite qualifiers, from March 22-27, when Ireland do battle with Serbia and Israel, as well as reigning champions and group hosts, the Netherlands.
IRELAND U-17: S. Morris (St. Kevin’s Boys); S. Long (Cherry Orchard), B. Lewis (Aston Villa), R. McConnell (Letterkenny Rovers), R. O’Reilly (Stoke City); K. O’Connor (St. Patrick’s Athletic), J. Daly (QPR), D. Murphy (Cork City); A. O’Sullivan (Home Farm), C. Wilkinson
(Millwall), J. Grealish (Aston Villa).
Subs: S. Coyne (Cherry Orchard) for Grealish (h/t), T. Mulroney (Crumlin United) for Murphy, K. McFadden (Norwich City) for McConnell (both 60), S. Byrne (Manchester United) for Daly (70), S. McCarthy (Skibbereen) for O’Sullivan, J. Leddy (Ipswich Town) for O’Connor (both 75).