Difference between Game pass and Gold live

Be sure that you redemeed the Gold membership on the right account and that your son is logging in with that account.

Are you sure that you got 1 year long and not 1 month long?

I suggest you to check on your xbox profile through your PC Browser and check your subscription to see when it expires.

Or you can go in System-Settings-Account-Subscriptions on your Xbox Console

That considered, let me explain you the difference between Game Pass and Xbox Live Gold

Xbox Live Gold gives you access to

Games With Gold (live "free games")

Deals With Gold (weekly and special discounts)

Access to online multiplayer

Xbox Game Pass gives you access to a vast library of games (including 1st party studios games on their day 1) that updates every month with tons of value.

Xbox Game Pass Ultimate sums up the Xbox Game Pass and Xbox Live Gold features and, furthermore, it gives you access to the Xbox Game Pass PC game library.

Game pass ultimate combines the two and gives additional benefits like exclusive game pass games

Gold = online. Gamepass = tons of games

A gold subscription allows you to play online.

Game Pass is kind of like Netflix for games. You get access to a library of games you can play. You do need gold in order to play online in those games.

If you still have gold, make sure you have the console set as your Home console so your son can access your gold subscription. https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

Xbox live gold membership gives access to multiplayer and chat servers. Game Pass gives access to around 100 games. The two are separate subscriptions.