My grandson is staying with us for a week and I'd like to download games from here for him to play alone or with me.

What do you recommend?

I believe the Freddy Fish series are targeted towards small children. Not sure exactly how small, though, so your mileage may vary.

Edit: Somehow none of these games seem to be here. Weird. I could have sworn I saw them... If you are willing to use another service to buy games, however, I stand by this suggestion.

By the way, the games are rated 4-7 so you should be good I guess.

If he can read, try Costume Quest, perhaps?

How and why would a 6-7 year old child not be able to read?

Off the top of my head, Rayman Origins would be a good pick.

Yes! I was just about to say that! Rayman series are a good choice. They look pretty good by modern standards (which I assume is a consideration since not many children are into "good old games".)

Also King's Quest VII would probably work reasonably well. Not sure, though if a child would have the patience to sit through an adventure game. Maybe with a guide.

When my son was eight, he loved playing and [url=https://www.gog.com/game/creatures_the_albian_years]Creatures (both now here on GOG).

I think they're targeted to like 4yr-to-12yr or somewhere in that range.

If you're willing to use steam, my 6yo loves Ibb & Obb, Crash Drive 2, and MX vs. ATV Reflex. The Lego games (some available @ gog!) can be fun too. Ibb & Obb and the Lego games are great becuase you can play in local coop.

they have pajama sam games for kids on humble bundle that would be great and the ray man series also stuff like minecraft is great. lego games as well

you will find the lego series and ray man stuff here but minecraft and pajama sam will be other sites

Ahem...

Triple town, Card City Nights, Ittle Dew, PixelJunk Shooters, Fez, Gex, Drod, Clarc, Tyrian.

How about Lego Harry Potter Years 1-4?

I'm playing this with my daughter. She is 8 though, but she loves it ;-)
The co-op is just great for kids!

I used to love playing Earthworm Jim 2 as a child, the first one would probably work just as well.