You don't have to do anything, just take it outta the box, hook it up to the tv and put your game in and they are good to go. However, I will advice that while you have your hubby or someone take the kids to the mall or something, you should hook it up, update it, create a PSN account if you don't already have one, password protect it (so your kids don't use your account and buy random stuff), do all the parental control stuff you want to, and maybe even load some money onto your PSN wallet so you can buy games digitally for them whenever you want to. You should give yourself a healthy 3 hours to do all these things then put the console back in the box.
When your kids get the hang of things they can create their own sub accounts on the console. Its just better to take the time and do all these things now rather than leave it till xmas day. Too much will be going on then to deal with half of those things.
In addition to FIFA and minecraft, you should consider getting them games like journey and child of light. Trust me, artsy, figure it out yourself great story games like that will open up their minds. They will force them to think, be creative, be open minded and instill an appreciation for pretty explosion free stuff... and did i mention fantanstic mucis too?