I have a Pisces Sun DD.
With both Sun and Moon in the same sign, your DS has a double dose of Pisces. So you are right, he will probably develop/display strong intuition, creativity, and an ability to be self-entertained.
Your DS was born around a New Moon. That is when the Sun and the Moon are in the same place in the sky. If he was born before the New Moon, his moon will be a lower degree number than his Sun. If he was born after the New Moon, his Moon will have a higher degree number. Make sense? I'm talking about the 30 degree's that make up each sign. So both planets fall between 0 and 29 degree's in the sign of Pisces. If they are within 8 degree's of each other it is considered a conjunction. The closer together they are the stronger this conjunction. Some astrologers will go out to 10 degrees apart for the Sun and/or Moon because they are personal planets. This
page has a description for both Sun and Moon in Pisces.
If you want more of an idea how this might manifest in your DS's life, determine if the Moon is a waning/basalmic or a dark/new moon. That will have a strong impact as well. Here is
another website from an astrologer that I've used to further my own studies via self-study. This particular post is about the dark moon phases.
Pisces' are beautiful. Be sure to nurture his sensitive, creative little spirit.