>>56289805I don't necessarily just want to say "do your own research" but there is a lot of research you can do on your own. While I trust you already know this, for the sake of covering bases; cards are released in named "sets" and each set has its own unique pool of cards that can be pulled. I think the first step is to consider what your son wants, i.e. what his favorite pokemon are. Next I would consider what you're trying to get out of it. Some sets have more valuable cards than others. You may think value isn't important when you and your son are just collecting what you like, but it's good to get the most out of your money in this hobby. An expensive card that you pull can easily be used to get one or several less expensive cards you might want more.
Typically googling set names can find you a visual gallery of the cards available in that set. tcgplayer is a useful website for market prices and is generally what all shops and players use for price reference. Type in a set name in tcgplayer and you can see all cards in it from most to least expensive. Search up the sets you've seen in stores and consider the balance of desirability and value to determine which set is most attractive to you.
As a personal point of advice, I would avoid Scarlet Violet Base, and Obsidian Flames. Obsidian Flames is especially tempting for kids cause Charizard, but both sets have very low market prices on their cards. You're always gambling on packs, but the biggest cards in these particular sets are so cheap that they're really not worth gambling for as opposed to just buying themselves. Obsidian's Flame's Charizard ex is only worth about 40 dollars, less than retail price on an Obsidian Flames ETB.