No, both are Windows games.

Not by any means. Both games demand rather powerful graphics hardware. It'll take some years until mobiles can handle that ;-)
GOG doesn't officially support mobile games, even though there are ways to get some old titles running, but it's often tricky. There might be more options once GOG expands its catalog of Linux games, but none of them will work out of the box on Android.

Btw, on each game card here on GOG you can see the minimum requirements for each platform (Windows, Mac, Linux), right after the description of the game. Additionally at the top of the page next to the game's cover is a topic "compatible with" which in case of the Witcher is "Windows (XP, Vista, 7, 8) and Mac OS X (10.6.8 or newer)".

If you're looking for games you can try running on your phone or tablet using DOSBox Turbo, you can check this list of GOG games that use DOSBox, although I don't think it's up to date:

http://www.gog.com/mix/games_using_dosbox

It also cites a wiki page that was apparently last updated in 2011:

http://www.dosbox.com/wiki/GOG_games_that_use_DOSBox

So there may be more.

But yeah, to reiterate, the Witcher games definitely do NOT use DOSBox and I don't think you'd be able to run them.

Thanks for the help everyone. I'm on vacation next month, so I can play them on my laptop while on the balcony overlooking the Gulf of Mexico. ;-)

I would advice against, as you won't see much of Mexico ;-)
Anyway have fun!