This recent article from TechRadar lists a mixture of apps and games aimed at 5-11 year olds, with ten Android and iOS tablet games and a further ten PC games. There are some engaging ones here, some requiring skills like creative problem solving and critical thinking - and others that are a bit more straightforward.

With lockdown in many countries around the world, any new - and free - apps and games for children are welcomed ... 

The article provides the following info on ratings, in-app purchases and adds for the listed games/apps:

Everything on the list is rated 3+, according to Google, and should be safe for even very young children. However, Apple rates most of these games with a more conservative 4+, except for Super Stickman Golf and Spaceteam, which are 9+. The games are all simple to control, easy to get into, and fun to play.

A note on IAPs and ads: Unfortunately, it’s hard to find a free game that’s not out to make a buck somewhere, so several games listed here will offer in app purchases for in game currency. And, some others will feature ads. In the former case, you can disable IAPs at a system level on your device before handing it over to a kid. With the latter, you should play the game yourself to ensure the ads are OK to show to your kid.