They can feel a bit small after hours of play on one Joy-Con. They are not incredibly fragile but they also don't feel anywhere near as resilient as a GameCube controller. The price is fair but shocking for one pretty decent controller that converts into two decent controllers.
All that said, they are the conduit between you and an exciting new landscape in gaming via the Switch. Amazing hand feel, havent had a single "de-syncing" issue. Wear the straps, be aware of your surroundings.
You know that kid is a little slow, maybe coach them along the way before blindly letting them have at it. As that is what will happen, they will have at it. You, and they will be laughing consistently and thoroughly.
These things are lit. Enjoy.