I started a new blog about being a dad and husband and all the adventures that come with it, and it has lots fun art:
http://www.ctupa.com/blog
Any feedback is greatly appreciated
I agree with the others, no harm in sleeping without a shirt. Who knows, he may grow out of it anyway.
My 6 yr old son likes to sleep in his shorts and polo shirt. I don't know why he likes but he enjoys it so I let him.