Depending on length of stay:
Our friends at the Murlough House assure us that traveling to Northern Ireland is about as safe as traveling to any other part of the world. There are no current security threats.
Ireland is famous for cold and rainy weather almost all year round. No matter when you travel to Ireland you can assume that it will rain at some point and you will most likely need warm clothes.
Keeping in mind that the Republic of Ireland is a separate country from Northern Ireland, the only requirement (for either country) is a valid passport.
There are multiple bunk rooms as well as a few private rooms. Bunk rooms have standard bunkbeds. Private rooms have double beds. You will sleep in bunk rooms unless special arrangements are made to reserve a private room.