There’s a decent amount of information out there. Some of it is rather objective, some of it is incredibly subjective. As you become more and more familiar with warrior talent trees, and how the talents map to in-game functionality, you will no doubt find your own preferences that match your playstyle.
If you look at the Protection tree, you’ll probably notice that a lot of it has to do with mitigating damage: Shield Specialization, Improved Shield Block, Anticipation, Toughness, etc.
A lot of the Fury tree is improving damage: Cruelty (adding crit chance), Enrage (+melee damage), etc.
And the Arms tree has a lot of utility: Tactical Mastery (keep some rage when switching stances), Sweeping Strikes (hit an additional target), etc.
You have access to all trees, but are limited by the number of talent points you have, to a maximum of 51 at level 60. And, as a warrior, you have access to all warrior skills, other than those that require being learned through talent points.
A lot of warriors don’t equip a shield a lot of the time when they are tanking, as physical damage mitigation isn’t as high of a priority as keeping a high amount of threat on mobs as possible; it’s easy enough for a healer to keep up the tank if its maintaining aggro.
So, depending on you and your wife’s playstyle and preference, you may find that you prefer smashing things with a two hander, dual wielding or using a shield and sword, and you may find that some of the talents in some of the trees are better suited to supporting that preference.
Elite’s Classic Warrior Tanking Guide is a great starting point, imo, for tanking instances in Classic.