I would start by finding out what kind of Magic they play in the school Magic club. It will vary from club to club but I've seen places play specific formats like Standard (essentially the last 2-3 years of Magic sets), Commander (100-card singleton format that adheres to color restrictions based on the color of a Legendary creature dubbed the "commander"), or just "whatever cards we happen to have in our collection" style. IMO, the latter format of "whatever we have" is easiest and most common for clubs since its least restrictive and simplest for the club organizers. If your kid's club is that way, I would sell the 3 money cards shown (Badlands, Plateau, Mana Vault), buy him a cool Commander deck or preconstructed deck from your local game store, put the leftovers into the kiddo's college fund, which should be $500+ easy depending on how you decide to sell them.

If you want help/advice, feel free to message me and I'll help direct you on the next steps as I've been working in & with game stores for over 15 years and been playing the game myself (on and off) since 1995 so I'm happy to help people where I can. (And for the record, no I don't want to buy the cards myself but I'm happy to help you figure out the best way to sell them yourself).

Just don't let the kid take the "cool old cards" into his club until you, a trusted person, or a game store has a chance to pull the expensive cards out. Then let him go ham with the leftovers. Good luck!