Hey Guys!
The good news is my wife finally started playing video games! (Thanks LoL, it's the first one she's stuck with for more than an hour or two) It's way more fun having a wife that plays LoL with you instead of bothering you during a game to sweep the house.

The bad news is she needs practice.

I like playing with her and she's smart, but she doesn't always do that well. Part of it is she's playing on a laptop etc. and the other part is she needs practice.

That said. When she plays I usually play a Tank, to try and help her stay alive longer.

I've found the following tanks to do well with her.

1. Rammus - The taunt and speed boost helps a lot.
2. Shen - Also has a taunt, Ult can save her sometimes.
3. Alistar - Heal and CC

I haven't had as much luck with Amumu or some of the other tanks as they don't have any form of hard taunt to get them off her and can get ignored.

I've tried Galio, but his Ult has such a long CD it's not much of a taunt.

I've tried Trundle with mixed results of his Wall of Filth.

I've tried Udyr with mixed results of his Bear Stance stun to help.

Does anyone have any recommendations for tanks other than those?

She mainly plays either Ahri or Riven. She's not super good with Ahri, because she hasn't quite mastered kiting / not running in an mashing buttons, but likes her anyways. She's done better with tougher characters like Riven or Shyvana.

I've had the best luck by far with Rammus. I just don't like him that much for some reason.

She's doing way better, but I'd like to help her (stay alive) as much as possible. Being dead and losing isn't as much fun.

Any advice is appreciated!

Edit: We only play Dominion which is why it's posted here.

My wife would sooner remove her nails with a pair of rusty tweezers than play LoL.

Amumu has a relatively short CD stun (max Q first if you haven't tried lololol), you can try that if you good with skillshots. But Leona is the real deal for continuous CC.

Lulu/Janna are the best at keeping allies alive, more so than tanks because they directly shield your ally and can cc enemies very much more often than most tanks.

Play on a smurf account with her, playoing other roles are one of the fastest ways to learn so make sure she switches it up once and a while.

I think I should clarify my question too.

What is your opinion on the best Taunting tanks or high DPS tanky characters to help my wife in LoL.

A hard taunt is good or such high damage that they have to focus me.

Blitz might be a way to go as well. Just about as much CC as you can pack into a champ. Lulu is also effective at mitigating enemy damage.

I play with my girlfriend, and we play exclusively Dominion. She has had a lot of luck playing as Warwick. He's pretty simple to learn, and he gets pretty tanky, That would be another alternative.

I would recommend Yorick. He is quite tanky and casting his minions is pretty easy and they even follow the enemy around beating on them. Bonus!

He's also very powerful both bottom lane and decently good top. His mana problems aren't a problem in Dominion and his Revenge Ult ability is satisfying, or in a teamfight he can clone the nastiest AD champ.

Build-wise, I recommend 2 AD, 21 defense (movespeed&CDR), 7 utility (good hands and movespeed), AD/lvl reds, armor yellow, MR/lvl blue, AD quints. Though anything works to be honest...I just prefer the MS and decent CDR.

I'd start with a Pros Blade and boots, for both top and bottom.

I recommend Ionic Boots and a Brutalizer for his first few upgrades which give him massive CDR reduction and good spamming ability.

From here you can figure it out. I get Negatron for MR, TriForce for general buffage, and Odins Veil for more defense.

Another fine, more defensive approach might be:
Pros blade, ionic boots
Glacial Shroud
(then in whatever order....)
-> Frozen Heart
Phage -> Frozen Mallet
Negatron -> Odins Veil
Hexdrinker -> Maw

I had this dilema as well with my ex-girlfriend when we used to play LoL. My objective was to pretty much make her play experience more fun, which can be equally as fun as trying to carry and rack up the kills. Based on what you have said, I believe the best person for you to play would be Leona. I know you said you aren't fond of playing female champs, but sometimes you have to let that feeling go for the type of champion you'd be playing. In my opinion, Leona is without a doubt one of, if not the best champion to play, when your goal is to help another teammate be successful. Between her passive which gives your wife bonus damage if she is hitting your targets as well as a full CDR/tank build (best imo) you will be an unstoppable stunning tanking rooting slowing machine. With max CDR, Leona can keep several people locked down for a LONG time, throwing out stuns left and right and flying around a mini-team fight (you and your wife) with the greatest of ease. Trust me, playing a female champion is worth it for the amount of utility you would offer to your wife. Although she has no literal "taunt", it is hard for the enemy to choose a target when they can't take any action at all. Give her a try!

Nautilus is fairly mobile and very tanky, I have tons of fun locking people down for my allies and he does have a somewhat respectable damage output even if you go mostly tank.

Malphite is a very scary tank and completely shuts down any autoattackers or heavy physical damage dealers, and has pretty good damage stats to boot (when built right anyway).

Maokai is scary in dominion because of the fact that he's basically perma-proccing his passive in any fight of size, is very tanky, and brings an interesting mix of support and damage to the table.

I also second the Leona recommendation, though I feel that she trades too much for all that hard CC IMO. Low damage, next to no innate kit survivability.

Jax has basically the one combo of pre-charge dodge while you jump at someone, but other than that is very high damage output, pretty tanky, and mostly a "mash skills as they come up" character.

Wukong could work for either one of you: high damage, strong innate survivability, CC on ult.