I have a 3.5 month old son and on Saturdays, my wife is out of the house for about 4-5 hours in the morning/early afternoon.

While I'm fine with keeping to his eating and napping schedule, I'm trying to think of more creative things that he and I can do together other than reading him the same baby books, doing tummy time, or propping him up on my lap to watch the soccer!

What other solo dad/son activities have you found useful and enjoyable for babies this age?