R.S.
You have lots of good ideas, my other idea is a book with songs that go with. My daughter loves "Pete the Cat." There is a corresponding website that read the book along with singing.
Also, you have probably done this, but I think the time of day and routine helps too. Maybe bringing them out when he is very calm/tired like before a nap or bed could help too.
I also like the ones with lots of pop ups and tabs to pull too.