Wifey was given a laptop and I was going to put some games on there for her. For some reason she was enthralled watching me play OTTTD, but I was looking for anything else that's TD or easy to play for those that don't possess the gaming ability that I, the husband does.

So far I've got:
Kingdom Rush
Defender's Quest
OTTTD
Kingdom
Stardew Valley

I'm considering games like The Banner Saga if it has difficulty adjustment.

I'd rather not mark this as a question, as I'm sure the constructive comments will have differing suggestions.

edit: shoot em ups with persistent upgrades are good too.

When It comes to TDs, my favourite games for PC in no particular order are:

# Defense Grid: Awakening
# GemCraft: Chasing Shadows
# Fieldrunners 2

The UI for Fieldrunners 2 on PC is very mobile-ish, but the game is great. It works best on touchscreen though.

When it comes to shoot em ups, maybe Jets n Guns is what you're looking for.

stardew valley can get a bit complicated with item management (atleast the way i play it) but gives a good indication of game requirements. you could try

yooka laylee - it's pretty casual and bland. i don't think the videos actually do justice as to how bland it can be so just be weary.
little nightmares - it's very casual and no jumpscares but it is a horrorish game. very enjoyable.
kingdom rush 2 - more of the same
brothers a tale of two sons - pretty casual. possible depressing too
unreal tournament 2004 - casual killing / lan

I really liked Alien Shooter TD and would add that to your list (sadly not on GoG). Highly recommend Defender's Quest, the story is pretty nice as well.

If there's any chance she might enjoy puzzle games, I'll always recommend Hexcells though GOG doesn't sell it. It's pretty close to the perfect puzzle game.

For slightly more active TD games, you might want to look at the Orcs Must Die games which are also not on GOG. Bleh. You already have mentioned all the ones I'd recommend that GOG offers, I'm not trying to get to to "switch sides" to Steam ;)

Thanks so far :)

I am a huge fan of finding tower defense games / casual easy games to play do check out these games, i had great fun playing them and hooked me into playing more games in the series.

Plants vs zombies

Hero of the Kingdom

Super Sanctum TD

Dark Fear

King's Guard TD

Botanicula

Evoland

Kingdom: New Lands

Feeding Frenzy 2

I have played all these games on steam i think some are on gog as well

Quite a few good games have already been mentioned so there is no reason to repeat them. Absent however are two games which are worth recommending as well.

*) Sang-Froid: Tales of Werewolves which is not only a very good game but also free. The devs made the game free a while ago to get attention for their new product.

*) Deathtrap which is an expanded version of the tower defense mini-game from The Incredible Adventures of Van Helsing (which is also worth getting if you like Action-RPGs).

You should definitely check PixelJunk games:
https://www.gog.com/game/pixeljunk_monsters_hd
https://www.gog.com/game/pixeljunk_shooter
the latter includes very good co-op!

Legion td 2 is one of the og tower defenses from war3 being remade into its own game.

3 of the best TD games have not been mentioned yet:
GemCraft: Chasing Shadows - http://store.steampowered.com/app/296490/
Bloons TD5 - http://store.steampowered.com/app/306020/
Immortal defense - http://store.steampowered.com/app/298360/

In addition, I would like to add:
Creeper World games - http://knucklecracker.com/
Train Valley 1 (and 2 is in EA) - http://train-valley.com/tv1.html
Puzzle Quest - http://store.steampowered.com/app/12500/PuzzleQuest_Challenge_of_the_Warlords/
Steamworld: Dig - https://www.gog.com/game/steamworld_dig

also check out Big Fish - https://www.bigfishgames.com/

Perhaps you should also consider simple point and click adventures made by Artifex Mundi (Nightmares from the Deep, Enigmatis etc.). For me they're just a definition of relax and casual gaming with nice music and charming visuals.

Revenge of the Titans is the best tower defense I've ever played. It starts off pretty easy, but eventually becomes incredibly difficult. Gave up about 80% into the campaign. I should try it again come to think of it.

And if you're looking for a pretty accessible game to play coop, then there is just nothing that beats good ol terraria