To want ds to play by himself for 20 mins?

[Spookey80]

I know it's not really Aibu but posted here for traffic.
Home on mat leave waiting for dc3 to arrive and just started thinking about how ds will manage when I'm feeding the baby. Ds plays with his toys when I sit with him, but just won't play with them on his own. He has the usual amount of toys, a garage a table with a train set, a whole playroom full of different stuff. I'm
Ds is 3.5yo, and will play independently with his sister when she's home from school (5yo).
Am I expecting too much from him? Any hints or tips to how I can get him to be a bit more independent in the house? Don't want to resort to telly to much.
Tgks

When my dd was born my ds was 2.5 he had his own bedroom and I turned into a giant play pen. I made it safe put a stair gate across the door and put him in there with music and toys and he was fine and safe and I could feed my dd in peace without having to chase him around and disrupt baby feeding. It worked well with ds1' dd1 and ds2 . I stated off with a new toy he hadn't seen before when baby was born and he soon got used to being on his own. Your not expecting to much from him at all.good luck