Hey there!
Well, sounds like our family is a bit similar – I have a 6yo (almost 7 now), 4yo, 2yo, and am expecting a baby (3 days overdue….)
What I did for my 4yo was added in a couple of subjects for her own…. now keep in mind she is pretty advanced…. and was pretty much demanding her own schoolwork… I did the MEP Reception math with her the last few months… It isn’t something she can do on her own though… And we did some reading instruction. I have just recently started a handwriting program with her, as she was asking for that too.
Basically, I would do some reading to her, then she would play with the 2yo. My 6yo son has his work in a “workbox” – so the order varies a bit from day to day…) After my son did his math, he would get a break, and I would do math with her. She would generally do some drawing then, while I work with my son on more stuff. After he did reading practice, I’d do reading instruction with her while he had another break. Same once handwriting/copywork would come up. She was generally quite happy to play while I worked with the 6yo as she knew her turn was coming.
I am hoping to get a few montessori activities setup during the summer for the 4yo and 2yo to do next year…. if you have the right activity setup for them they can keep busy with it for a LONG time. For instance, my 2yo was fascinated with diaper changes, and was pretending to change her teddybear – so I gave her a new diaper (one that was too small for her, but would be too big for the newborn for a long time) for “Fluffy” – and over the past few weeks she has diapered her teddybear for hours – generally a good 30min at a time. She is also spending a lot of time folding a dishtowel over and over (that is an activity she started on her own – there was a dishtowel out, and she folded it!)
Whether the workbooks are worth it depends a lot on the child. I had a couple of those for the 4yo (then 3) at the beginning of the schoolyear – and although she seemed to enjoy them, she didn’t always do it the way she was supposed to and she tended to rush through them. (ie, we had one that was for colours – so the instructions, which I would tell her, would be something like colour the carrot orange. She would often do whatever colour SHE wanted to do it, or would just scribble 2 or 3 orange marks into it and call it done. For the mazes book, she would sometimes do the maze, or sometimes do the maze, but going over the lines….)
She was happier to be given some water colour paints and a piece of paper. Or given scissors and a blank page to cut into little pieces.
hth some!