You write that your day used to be very planned and organized, and that you had time for workouts, meditation, reading books and other stuff. In addition, your question was migrated here from Personal Productivity.SE.
My first guess would be that you didn't have much slack built into your routine. Might that be right?
I am all for improving your organizational skills, as most other answers here suggest. But if you are already an experienced SE user, you likely already are pretty organized, and you may have hit a point of diminishing returns here. In addition, if you don't have much slack in your schedule (note that there is no TV in my example above), then there is little fat to cut.
The day only has 24 hours. If so far you used 8 hours for work, 8 hours for sleep, 1 hour each for your commute, for your workout & personal hygiene, for surfing StackExchange, for talking to your spouse, for meditation, and for doing chores (6 hours in total), and finally read books for two hours every day, then you have planned for every single one of these 24 hours.
Time does not grow on trees, and there are only very few "grownup" things that you can actually do together with a kid. Yes, as Kramii suggests, you can do a workout by running with a pram or weightlifting your toddler, but this is neither a very good workout nor really quality time with your kid - it's a least bad combination.
Bottom line: some "grown-up" activities may need to go if you want to have N quality hours with your kid(s) every day.
Sorry for being blunt about this. I have twins, and I had a hard time learning this. I had exactly the problem above: I am already pretty organized, and I had few low-worth activities in my daily routine that I could cut. I had to cut down on "grown-up" activities, and I still miss some of those. I have reduced my reading time, I haven't learned a new language in years, I used to publish scientific articles and cut down on that a lot, and for a while I reduced my job to 80%. I honestly wish somebody had told me that openly and brutally earlier on - it might have made the transition easier on all of us, including my wife.
So: take stock on where you are. Look at what you are doing at this point. Decide what "grown-up" activities you want to keep (communication with your spouse should be high on that list), which activities you want to cut back on, which activities you can meaningfully do together with your kids, and which activities you will need to suspend for the time being.
On the bright side, some "kids'" activities are a lot of fun for grown-ups, too ;-), and as your kid gets bigger, you will be able to introduce him to the things you cut back on. For instance, my twins are starting music lessons now, and I finally got back to the piano after a multi-year hiatus. And of course as your kids get older, you will be able to get back to (some) activities you had to suspend for a few years. Take a long term view of things.
And of course do get as organized as possible.