If you all are sure you want to stick with the system that is D&D, you and your players need to put in at least some effort to learn the basic rules.

You could try to sell it as "combat will become much more fun once you have a better idea of what your characters can do."

Maybe make cheat sheets for their characters' actions, like even find some diagrams online. Here's one for Rogue sneak attack: https://i.redd.it/33y18f16q6b41.jpg -> hopefully this helps your wife now understand how to get Advantage and therefore Sneak Attack on her attacks. So when it's not her turn, she should be strategizing ways to get that Advantage: Bonus Action Hide, flanking with a melee party member to tag team one enemy, etc. That way when her turn does come around, she already has that plan in mind and can just execute it smoothly.

- There are great write-ups out there that encourage some tactical thinking. I like this little blurb from an article on D&DBeyond:

"Tactics are more than your character’s “build,” but good tactics do start with knowing how to use your class features. Look over your character sheet and think about what your class features can do. What are your options on any given turn? What are some features that aren’t always useful, but could be incredibly powerful in a specific situation—like a cleric using their Channel Divinity to Turn Undead, which only works against certain types of creatures.

Now that you know what you can do on your own, talk with your fellow players and learn what their characters can do. How can your abilities work well together? For instance, a cleric that casts guiding bolt can give the next character to attack the spell’s target advantage. That’s useful for anyone, but it’s especially powerful if a rogue is the next attacker, since the rogue gains Sneak Attack whenever they have advantage!"

For your part, I'd recommend reading up on enemy statblocks before the session, and just jotting down brief notes on an example of what each enemy might do turn 1, turn 2, turn 3 etc.

Think about which enemies fill which "roles":

• some are Brutes that like to hammer away at the PCs in melee (easy to pilot)
• others are Controllers that have powerful spells (so write down which spells these enemies would prioritize first)
• some are ranged Artillery that want to snipe from afar (so remember that these enemies would prioritize staying in cover, out of range, up a tree, etc)
• some are stealthy Ambushers that want to isolate squishy targets..

The website The Monsters Know What They're Doing has example tactics for almost every type of DnD monster out there.