Xbox – Downloading DLC on XBL with a Silver account

I would suggest buying your son a prepaid card. You do have to remember when it runs out and buy another, but they tend to be $10-15 cheaper than buying the same amount of time through Microsoft directly. It's also much easier to stop being a subscriber, since you just don't add more time to the account - no need to figure out how to stop the automatic payments.

When you purchase a game from XBLA, that game is licensed in 2 ways:

1. To the account you purchase with it.
2. To the machine that you purchase it on.

Seeing as you purchased those games on another machine, that's why it is requiring you to be online to verify those games are licensed to your account.

What you need to do is transfer content licenses to your console. It is a multi-step process, and you need to be with your new machine as you might need the Console ID, but it's fairly painless and quick. The full instructions and some videos for the license transfer are found at www.xbox.com/drm.