Transatlatnitc cruises meens alot of days on sea, no ports to get out.
Plus when you have kids that means you need ship with as much activites available as possible to avoid boredom.
Century is fairly good ship for that, though I think one of RCI mega-ships with endless possibilites for entartainment woud be even better.
Research on internet details about your ship.
Also consider posibility of having rough sea. I hope not but it could happen.
Check with your local doctor what can you give the kids in case of seasickness.