The site has a fairly simple design -- kids click on a game and get a URL to send to friends that leads to a dedicated room where everybody plays the game. On Playingcards.io, players' screens are synchronized, so you see cards and game pieces shift in real-time as other people move them. (Other players won't see your cards, though.) The game board is somewhat customizable -- players can add card holders, extra decks of cards, and other items. Although the site recommends having eight or less participants and says a limit will probably be added in the future, as of now, there are no restrictions on how many people can play a game. Rooms are automatically saved and won't be removed until they haven't been used for two weeks -- so if kids don't finish playing, they can revisit a game later by just entering the URL.
Some games, like Euchre, include instructions. But others, such as chess, are missing directions of any kind, so kids will need to understand the rules before playing. Kids are also responsible for some of the main functions in games. There isn't a way to have cards dealt automatically as of now, for instance, and in some games they'll need to keep track of the points players are earning. Kids also need to determine when a game ends. They can't chat on-screen, which would make those and other aspects a bit easier, and kids who come to the site hoping to access the online version of Cards Against Humanity that PlayingCards.io offered earlier this year may be disappointed to find it's no longer available. With more than a dozen other choices, though, as long as kids are OK with supervising the game's direction, they should be able to find plenty of items to play with friends.