You've had some great suggestions already.
With my DS2 (12 weeks) I take him to all of DS1 activities. While he doesn't really participate he gets to see what's going on. I also spend some time each day with the him looking directly at me. I mimic his facial expressions and sounds. I spend a lot of time talking to him and explaining what I'm doing. We do lots of reading, but that's mainly because DS1 loves reading 😃