Reading eggs is supposed to be good, expensive though. Apparently you can only buy a 12 month license, rather than own the game. Try Schoolbo, same vein but not quite as good.

You could try searching things like puzzle games, math games, fun games, animal games etc for children. Play anything you download yourself for a few minutes before handing it over to the child. Try to avoid literacy/spelling type games, apart from those mentioned, as they are normally developed in the States and use American spelling.

Thank you.  I have downloaded some games fromm googleplay.  They nearly all have in-app purchases and some have pop-up advertising. I have tried some of the games after I downloaded them and then I couldn't get them to go back to the beginning. They saved the level I got up to.

I didn't think it would be so hard to find kids games that don't have ads, and you don't have to pay to unlock more levels or get items.

Some of the items are over a hundred dollars ! Even games you buy press you to spend more in app or to remove ads. 

Bugs and Buttons looked good but the ezpad wouldn't let me download it  The ezpad came with mofi software. It has it's own 'store' I tried downloading something from there and the game was in chinese! 

I get games from Big fish I've been a member for years if take yearly membership which requires you buy 1 game per month for a year games will cost you approximately $7 each depending on the exchange rate. Payment is available by paypal.

The games are all types and all age ranges for all different formats the range classed as family games would be most suitable for your purpose.

Once purchased they are yours for life and can be downloaded multiple times for multiple computers or tablets etc from your purchase history.
To start from the begining in these type of games you just need to start a new game under a new profile.

Be sure to only buy  games suitable for the media you're using it on .

All are available for trial before you purchase