Need advice on setting up a new Mac for someone else.

Just want to reinforce what @BobTheFisherman already recommended, so you understand it's not just one person's opinion. Let your son set up the new MBPro. Don't do it yourself.

He should do the initial setup using his own Apple ID and set up his own initial account on the Mac. The first account created on a Mac is significant and if you remove or modify that account you will run into future problems with upgrades and other security related matters.

Do not install applications using your own Apple ID; your son needs to use his Apple ID for that. Apps from the App Store are associated with the Apple ID that installs them. Even if you have Family Sharing set up with you as the Family Organizer, your son should still be the one to install the shared apps under his own Apple ID.

There are other reasons, too but I hope you have gotten the idea why it's best for your son to do his own initial setup of the Mac you want to give him.

It's a nice thought, but I'd let him set it up if I were you. He needs to set it up with his own Apple ID anyway but he also needs to use Migration Assistant or a Time Machine backup (if he has one) to set it all up so it will bring across all his apps, docs, settings, etc. If you set an account up for him then he won't be able to migrate properly and will probably end up restoring the Mac from scratch when he gets home because of permissions issues and such. The risk of it going pear shaped is high. If you're going to deliver it personally you can help him set it up from his current Mac when you're there.

It's a lovely thought to deliver it pre-configured but I imagine he's going to be chuffed enough at getting a new Mac from you.

The best (and most painless) way to set up a new Mac is to have the new owner use the BACKUPs of the old Mac as the source for everything.

Very early in the Setup Assistant, you get a screen that wants you to enter a new Admin username --- OR ---

Point it to where existing data already exists (an older Mac or its backups).

The way you could make this easy is to nudge them to have recent backups when you get there.

If you create the account on the new Mac before using migration assistant then you can create permissions problems. The account names will be the same on both Macs but the account ID won't be and so the new account won't have the correct permissions. There have been recent threads here from people who had done just that and were having problems because of it. Leroy's and Grant's advice is good - trust the Apple process. You don't want your son's main memory of his birthday present to be the 3 weeks of hassle and telephone calls it took to get it working glitch free.

Alfredo Jahn wrote:

Need advice on setting up a new Mac for someone else.

Before you say "let him set it up", I get ya. H̶e̶ ̶w̶i̶l̶l̶ ̶b̶e̶ ̶a̶u̶g̶m̶e̶n̶t̶i̶n̶g̶ ̶t̶h̶e̶ ̶i̶n̶i̶t̶i̶a̶l̶ ̶s̶e̶t̶u̶p̶.̶ ̶I̶'̶m̶ ̶j̶u̶s̶t̶ ̶t̶r̶y̶i̶n̶g̶ ̶t̶o̶ ̶s̶a̶v̶e̶ ̶h̶i̶m̶ ̶s̶o̶m̶e̶ ̶t̶i̶m̶e̶.̶ ̶

The most trouble free way to move to a new machine, is using the Setup Assistant on the initial boot of a brand new machine— you have one shot here. Set up your MacBook Pro - Apple Support

The second best way is use the Migration Assistant.

How to move your content to a NEW Mac: Transfer to a new Mac with Migration Assistant - Apple Support

Let him open the box and set up his new machine. Any other way you are just creating headaches and wasted time.

Full Stop.

Sorry but there is no way you should "set up" his Mac. I know you don't want me to say it but "let him set it up". If you set it up, he will spend time resetting it for his needs and preferences.