You're welcome. That's a tough situation (but a common one). The main things I can thing of right now are:

* continue to be a good example
* try to reduce stress in her life (without increasing yours significantly)
* be a good listener
* consider a physical hobby together like swing dancing -- or maybe walking or swimming or yoga or kayaking in the sunshine (ideally things your kids can be safely involved in too)
* consider humor (healthy humor; maybe read up on that like stuff by Joel Goodman such as "Laffirmations" or things by others)
* consider a temporary change of scenery (like an active vacation in the sun?)

Kudos on your own success though. That has to be helping your wife even if indirectly in being able to be a better parent and better spouse.

One idea is like on airlines: "Put on your own oxygen mask first before assisting others". You've already done that, but keep it in mind. As Zig Ziglar said, "People often say that motivation doesn't last. Well, neither does bathing - that's why we recommend it daily." Also, a lot of this for everyone is a spiral -- or ups and downs with backsliding. It takes practice (and mistakes) to get better at things. You might find of general interest two somewhat funny movies by Joe Cross called "Fat Sick and Nearly Dead I and II". They talk about progress and backsliding and progress again in nutrition and exercise. They might be useful in knowing you are not alone in that sense.

You can try to structure your shared environment (also to your own benefit) to make doing the healthier thing easy to do. Like maybe figuring out a better way to open and close curtains -- maybe even something automated? Maybe consider a treadmill workstation (although it requires reasonably good eyesight so works better at younger ages with more flexible accommodating eye lenses). The pandemic makes socializing harder of course, but maybe think about how you can help your wife more easily stay connected to any friends or family she already has (even one phone call a week).

Also, a gift card for yoga in a way just adds to your wife's workload (including travel to and from lessons). So how about getting a yoga mat and doing yoga together at home? Again, setting a good example yourself could help. As is the idea of making doing the healthier things easier.

Since the issue (including nagging) may affect your relationship eventually, consider pre-emptively reading a John Gottman book like "What Makes Love Last". Maybe also check out this HN discussion and story on "Beware of Being "Right"" to avoid crossing over from being supportive to being controlling: https://news.ycombinator.com/item?id=23802241

Also, rather than nag given it is not working (but still may make you feel good that you are trying and so be reinforcing to you), consider saying nothing about what you think should happen but instead providing some sort of positive reinforcement for your wife when she actually does a healthy thing -- even a small step. Look at writings or videos by dolphin trainers or positive-reinforcement-only dog trainers, like perhaps Karen Pryor. People are always doing a variety of things, so look for the positive tiniest incremental improvements and help them grow. That will also help you yourself focus more on looking for the positive things your wife is doing than the negative.

Or, at a higher cognitive level, since you are interested in influencing decisions, you could also look into books on selling, like Dan Pink's "To Sell is Human". From the blurb: "To Sell Is Human offers a fresh look at the art and science of selling. As he did in Drive and A Whole New Mind, Daniel H. Pink draws on a rich trove of social science for his counterintuitive insights. He reveals the new ABCs of moving others (it’s no longer “Always Be Closing”), explains why extraverts don’t make the best salespeople, and shows how giving people an “off-ramp” for their actions can matter more than actually changing their minds. Along the way, Pink describes the six successors to the elevator pitch, the three rules for understanding another’s perspective, the five frames that can make your message clearer and more persuasive, and much more. The result is a perceptive and practical book–one that will change how you see the world and transform what you do at work, at school, and at home."

Yoga nidra or positive visioning might also help if your wife does want to change something?

If you can address one aspect, which should it be? I'd suggest sleep. That can be a huge challenge with young kids. Try reading "Why We Sleep" by Matthew Walker. Or maybe listen to it as an audio book? What I got from that book was a sense that our brains are adapted to run overclocked (as it were) during daylight hours, building up waste products and also accumulating unstored memories. When we sleep well, channels in the brain literally widen and fluid flows to wash away the toxic buildup (which otherwise can contribute to Alzheimer's), our brain moves memories of the day into long-term storage, or brain via dreams also processes traumatic events of the day to remove the distressing emotional overtones and learn from them. But that only happens with good sleep. So, ask yourself, how can you help your wife get better sleep? You can also ask yourself if maybe she is a night owl trying to keep a schedule better for a morning lark or vice versa?

Anyway, some ideas to get you started. Now that you are thinking more about this, all sorts of ideas might come into your attention. Still, in the end, no one is perfect (if such a thing is even definable given conflicting -priorities). So take time to enjoy your imperfect relationship with your imperfect wife and imperfect kids -- and try to be thankful every day for how lucky you are given you are imperfect too (as is everyone in some way). That might help reduce some of the stress of the situation for everyone -- which might have its own beneficial effects.

Good luck!