We have no kids yet, but planning for one this year. I know it would get tight to work on side projects with a kid while being actively employed, but it is still very possible to get it all going. We just need to optimize a lot, and learn to ignore/skip unimportant things. I know a few people who have run companies with little babies in their families.A lot of people I've met in the Bay Area successfully did it with 2 kids and a wife and a full-time job. Your side projects don't have to stop with kids coming. One thing I know that would help is, find a lightweight job while you're fiddling with side projects. That will help ease it up a lot. Another tip, wake up early in the day at 5:30AM or so. It will give you a lot of time on a super sharp mind.
I think it is doing "these 2 jobs" that is the main problem here. If my side project spawned into a company that I am able to let go of my full-time job, I am sure I'd get extra time to dedicate to my family. I am frankly looking forward to that day. In your situation, it would be your job to speak your heart out with your wife. Regardless of how financially viable your side projects are, they are still something you enjoy and you must communicate this to her clearly. She should be able to understand AFAICS.
I regret not doing this sooner when I was single, but I am doing it at least now. I am more experienced and more skilled today than I ever was.
Working out helps me a lot and allows me to refresh and get more capacity. Sure, there are days where I'm squeezed out, but enough sleep also helps. What I've also learned is, use anything you have to, to get the job done and don't focus on optimization and scaling problems at all. Make sure to throw away features that don't add any value now and always keep that in mind. If you are careful about these points, you can certainly accelerate.