Things to do with baby

FTM here and having never really been around babies I'm a little bit at a loss of what to do with my 11 week old for play.

We do tummy time, read books, he has a swing with toys overhead and a play mat with toys overhead. I spend a lot of time walking him around the house so he has a change of scenery or we look out windows. When its nice out we go for stroller rides. Which sounds like a lot but I find I don't know what to do with him at times.

I dont like just lying him down to play with the toys overhead as I'm terrified of him getting a flat head so I try to keep him off the back of his head outside of sleep and naps.

Anything else you can ask suggest for me? Thanks!!