I'd like to bring some specific experience here: I'm a Pokémon league organizer for a league of 7-8 year olds (pre-pandemic, and hopefully again post!), and a parent of two children who collect, and play, Pokémon cards.
The answer here depends greatly on the child. The most common thing a child would do with Pokémon cards, of any value or type, is to bring them into school or to the playground, and show them to their friends. They're cool things, they know they have some inherent value, and have cool moves and such. Maybe they play some sort of game with them - usually not by any real set of rules - but mostly it's just showing off, and maybe trading.
Very few children at 7, but not zero, are aware of the larger environment - the industry around the cards, from tournaments with significant prizing, Twitch/Youtube streamers, and the like, to the collector scene with real, generally increasing value in rare cards.
The question is, then, what the child wants this card for. If he's one of the rare 7 year olds truly aware of the scene and aware of the value of cards, then it's probably fine to give him the expensive card with a warning to keep it safe, and probably give him a proper case (like a screwdown), or even get it graded (maybe give it to him, with an offer to get it graded). He'll appreciate it!
But if he's one who prefers to take it to the playground, as most will at that age, I would be assume it will be gone. Most likely not just damaged - odds are someone will take it from him at some point, or he'll trade it, or lose it. If he's showing off a card everyone knows is valuable (which is the point, right, or why show it off?), say a Shiny Charizard VMax or something similar, then there's a good chance no matter what you do with it, it will be lost or stolen - a screwdown won't help there. Either don't give it to him, or be okay with this - if he wants it because it means he can show it off, it's silly to give it to him and tell him he can't.
Finally, there are a few kids in the middle. I'd put my eight year old there. He likes cards, and does have some valuable ones he's lucked into. For the truly valuable ones, I do one of two things: I either directly pay him for them, which often he's happy to have the value, and then I add them to my collection; or I put them in a binder for him, but not one he shows to other people. He knows he has the card - but he doesn't care too much about showing it off. That's the middle ground, and if you do have a kid in this area, it is worth it to consider giving him some help keeping it safe - it's too hard for a kid at that age to have sufficient impulse control, and frankly organizational skills, to really keep something safe, but you can add some help there. Maybe put it in a case and mount it on the wall.
In my experience, though, most kids are in the playground group. Do find out what he wants it for, though; then you can identify the best solution for him, specifically.