Yes Sluice, the action plan does mention increasing the population, but afaik there are "only" another 3K of the houses remaining to be built!
The trains have been extended in length so most days, apart from 2 particular times, you do get a seat from Balbriggan.
The nightlife is good, loads of young people, certain local establishments have very cheap drink. Others draw you in with pitcher specials (cocktails and beer, yum).
Childcare wise, there is a shortage of childcare everywhere, but considering you don't have any children at the moment, you would have the opportunity to put any children you may have on a waiting list, this is a luxury most young families don't have when they move to B'Briggan
Restaurant wise, the pickings are a bit slim, there would be very few for the number of residents, however i think this reflects the fact that our disposable income is being invested in our homes and not on meals out
Shops in the town include a Lidl, SuperValu and a manky Tesco, which would remind you of an old Crazyprices. Transport would be by means of the diesel trains, provincial service (Bus Eireann) which goes up the old N1 into the city centre and they have the Nightrider which is more direct than the Nitelink for a night out in the big smoke, and Dublin Buss (33) which goes into Swords and on into town.
I don't think that we would move close to the city centre given the choice. The quality of life is miles better, we have made some great friends and some of our family have followed us north as well, so we're never lonely. We open our windows and hear the sea; walk for 5 mins and we're on the beach; living in an extremely safe neighbourhood & wouldn't change it for the world.
Best of luck with your decision!