The City pair, along with Yaw Yeboah, were more than a match for Den Haag with the City trio forging an exciting front three.
Unal took his season's tally to five with goals in the 13th and 35th minute while Celina added another in the 54th in another impressive performance.
Staying in Holland, Shay Facey's Heerenveen clocked up a fine 3-0 win away to Roda JC with the City youngster's afternoon spoiled by a red card on 75 minutes, though none of the Blues' on-loan trio at NEC Breda as Ashley Smith-Brown, Brandon Barker or David Faupala played or were on the bench in the 2-0 defeat to Sparta Rotterdam.
Sinan Bytyqi was an 80th-minute sub as Go Ahead Eagles were beaten by Vitesse and Oleksander Zinchenko did not feature in PSV's 1-0 home loss to Feyenoord.
In Italy, Joe Hart kept his first clean sheet as Torino and Empoli played out a 0-0 draw.
In Scotland, Patrick Roberts played 75 minutes of Celtic's 2-2 draw with SPL basement side Inverness Caledonian Thistle before being subbed.
Former Celtic loanee Jason Denayer made his full Sunderland debut in a 1-0 defeat to Tottenham. The Belgian was a last-minute replacement for Patrick van Aanholt but couldn't prevent the Black Cats from losing again.
Wilfried Bony had little joy, either as Stoke were thrashed 4-1 by Crystal Palace.
Samir Nasri was absent from the Sevilla side that drew 1-1 with Eibar. Bruno Zuculini played for 62 minutes of Rayo Vallecano's 2-1 loss at Mirandes.
Back in England and none of City quartet George Glandon (Fleetwood Town), Callum Bullock (Crewe), Kean Bryan (Bury) and Jack Byrne (Blackburn) featured for their sides over the weekend, though Aaron Mooy again impressed as Huddersfield Town beat QPR 2-1 to maintain top spot in the Championship.
More loan updates through the week and a full round-up this time next week.