Depends what you call long haul. 6 - 7 hour transatlantic is fairly easy, small toothpaste and toothbrush can help freshen you up before descent, bring a book or magazine, almost all transatlantic planes have good entertainment, but Aerlingus is still operating at least one 1996 Airbus with drop down monitors - no seat back monitors. Their newer planes have great in-seat entertainment.
Dress in layers, if you are near a main door, you'll feel the cold. pack a snack too. if you're near the back you may not get your choice of meal.
BTW, Pasta always heats up the best, so order that if it's available. bring a bottle of water on board, the air can be dry. Ear-Plugs are also advisable provided you can get comfortable with them.
Don't wory about babies, they usually sleep, just cry usually during descent...
otherwise, sit back relax and enjoy the flight!!