Excellent footwork from Hindolo Mustapha saw him work the ball into the box and then pick out Reid who was unmarked to finish with ease into the far corner.
The Scot almost had a second in a matter of minutes after Rohan Ferguson in the Larne goal inadvertently played it straight back out to him, but the shot-stopper recovered in time to parry away the effort.
Larne grew into the half as it wore on, with Sean Graham firing narrowly wide of the mark after cutting in on his left foot, while Andy Ryan hit the side netting on the half-volley.
Izquierdo pulled off a solid stop to deny Bonis scoring right at the end of the half, and then had to do the same to deny Joe Thomson after the restart. He spread himself well for the first, while reacting brilliantly to stop the deflected second.
Larne pulled one back from a corner in the 53rd minute, as Cian Bolger rose highest to head home for the Northern Irish side.
Inver Park then erupted once more just past the hour-mark, with Ryan scoring an inch-perfect free-kick, which went in off the crossbar, from about 25-yards out to level the scores.
Momentum swung in Larne’s favour after the second, and a vital block from Jake Grante to deny Sloan stopped them from taking the lead a minute after levelling.
The hosts did eventually take the lead with 15 minutes remaining, as Thomson saw his strike on the edge of the box deflect in.
An effort from Jemiah Umolu late on wasn’t enough for Palace, as Larne held on to emerge victorious in the Jeff Hughes Testimonial.
Attention now turns to the U21s' final pre-season game away at Leatherhead on Tuesday evening - tickets are still available from just £3, click HERE for more info.
Larne: Ferguson (GK), S. Graham, Cosgrove, Hughes, Donnelly, Randall, Gallagher, Sloan, McKendry, Ryan, Bonis.
Subs: D. Graham, Brown, Cowan, Bolger, Want, Glynn, Devlin, Altintop, Thomson, Smith, O’Neill, Lusty, McAlister.
Palace: Izquierdo (GK), Francis (Grante, HT), Farquhar (Trialist, 52), Browne, Cardines, Reid, Phillips (Akinwale, 61), Nascimento, Derry, Mustapha (Umolu, HT), Marsh.
Sub not used: Eastwood (GK).