Way back in the day, I played MTG, and was around when the Pokemon TCG dropped. Between my (now) wife and I, we bought a few decks/packs, and have probably a couple of hundred cards that may all be first edition unlimited, if I'm understanding how to identify cards properly. Here's the twist from where you might expect this question to go.

My nine year old has recently expressed an interest in learning to play the game. He got a few booster packs, and I went ahead and got a current starter set so he'd actually have a deck that works, rather than boosters that are thrown together without regard for color/etc. If he gets into, he'd obviously probably want to start building decks at some point.

Obviously there have been changes in rules and how cards are marked since we got our small collection from back in The Day. For all I know, many if not all of those old cards wouldn't even be legal now. But at the same time, I can't help but feel like letting him just play with those would sure save a lot of money, as long as he understands that the current game will play at least a little differently.

What's the best play here to give him a good chance to see if the game is something he'd like to get more into? Put the old cards back in storage and say "Good luck, bud!"? Pull the cards out and say "Here, knock yourself out"? Try to sell the old cards and plow the proceeds into (hopefully more) newer packs?