Mine would watch CBeebies, colour in books, play with Lego (for hours) do large floor jigsaws. We had a large toy box which came out when they came down, with cars, dolls, a fold up dolls house, plenty of things to pull out and play with all day.
As long as I was in the next room they got on with it on their own, I would sit with them in the afternoon, after coming back from the swings, with a book.
Apart from that they were quite happy to play on their own.
Every day if fine enough I put them out in the garden to mess around in the sand pit, for a while or they would play with boxes or flower pots and a trowel in the dirt.
When I say ‘ they’ GD was the oldest and GS was a baby in the pram. As they got older they still played separately, each in their own little worlds.
However, early starts (and whilst they were babies, night feeds) are knackering, but I was only in my 50s then, I couldn’t do it now I’m nearly 70. Why not try to stay near but pottering about in the next room whilst he gets on with the serious game of playing on his own?