You could make a penguin birthday cake. I know it's kind of difficult to find being June, but maybe get some penguin figurines or even order some online (I don't know when his birthday is coming up, so I'm not sure how much time you have to wait for them) to put on a sheet cake. That way, after you guys are done eating it, he has something to play with! And what kid doesn't love that? Also, a trip to the zoo might be fun since it's warm
Hope that helped a little!