I'm self employed and my kids are home educated, so that involves a fair bit of work finding and researching activities they'd like, contacting organisers, working out travel arrangements etc, making sure we have appropriate packed lunch stuff in and then fitting my work around it all.
Then there's social stuff - parties (presents, cards, actually going to the things), making arrangements for visiting friends, hosting friends, planning trips, booking tickets.
Shopping for birthdays and Christmas, researching presents and planning and hosting parties, writing thank you notes, finding places to put everything!
I spend an inordinate amount of time on the library website (we have more than 60 books out most of the time), ordering books, renewing them, checking when they need to be back and still somehow paying fines (oh, and actually going to the library).
There's all the ad hoc stuff like sorting through clothes after growth spurts plus going shopping for or ordering new clothes; sorting through toys and taking unused ones to the charity shop etc; sewing up damaged soft toys; researching, planning and booking holidays and weekends away.
Most of these either take a while, but only every few months, or take a couple of minutes but it's relatively frequent, so added to the daily washing, tidying, cleaning, cooking, shopping and sorting things out, working and the actual spending time together, it's just the knowledge that there's literally always something that's waiting to be done.
Poor teddy has had a hole in the back of her head for months now, but she's got to wait until after the thank-you cards and robot dog research, by which time there will be another laundry mountain to tackle and another library book due for return! The headspace required to keep track of it all is the thing I find the worst tbh, but most of it is theoretically optional, so I can't really complain!