Susan asked: “What are free apps that entertain 10-year-old girls?”
Susan, most apps have switched to a freemium model, so, it’s likely that you will be able to find lots and lots of apps that would keep your kids busy for free, except they’re not free.
Most free games these days try to make money by selling you items or abilities after you download them.
For example, Kingdom Hearts for Android is a free game where you can meet and play with Disney characters, your 10-year-olds would probably enjoy it, but it does feature in-app purchases for as much as $99, sometimes those purchases are pushed as a way to get an item that is virtually indispensable to move on to another level, or even as a way to keep playing without having to wait minutes or hours to “recharge” something that acts as an in-game payment for another turn.
iOS has the same problem, Spiderman Unlimited is a fun infinite runner that features male and female characters, your 10 year olds might like it, but you need to either be patient or pay for extra turns. When you get to a certain level you also can’t move on without your team reaching a “tier” first, the further you go the higher that tier becomes, and the harder it is to reach it without paying.
Disney Crossy Road is another popular game, it’s also free, and it’s basically Frogger with Disney characters, but again, there are in-app purchases.
You can look at the most popular games on the app store of whatever platform you’re on and the vast majority of them will be just fine for 10 year olds, but make sure that either in-app purchases are locked down via parental controls, or that they understand that they shouldn’t be spending money on the game.